diff --git a/src/main/java/com/fowoco/server/audit/domain/AuditAction.java b/src/main/java/com/fowoco/server/audit/domain/AuditAction.java
index 55f4569..3302300 100644
--- a/src/main/java/com/fowoco/server/audit/domain/AuditAction.java
+++ b/src/main/java/com/fowoco/server/audit/domain/AuditAction.java
@@ -3,6 +3,7 @@
 public enum AuditAction {
     TASK_CREATED,
     TASK_UPDATED,
+    TASK_ASSIGNEE_CHANGED,
     CHECKLIST_ITEM_UPDATED,
     TASK_CANCELLED,
     APPROVAL_REQUESTED,
diff --git a/src/main/java/com/fowoco/server/task/api/ChangeTaskAssigneeRequest.java b/src/main/java/com/fowoco/server/task/api/ChangeTaskAssigneeRequest.java
new file mode 100644
index 0000000..a4c377d
--- /dev/null
+++ b/src/main/java/com/fowoco/server/task/api/ChangeTaskAssigneeRequest.java
@@ -0,0 +1,24 @@
+package com.fowoco.server.task.api;
+
+import com.fasterxml.jackson.databind.PropertyNamingStrategies;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
+import com.fowoco.server.task.application.ChangeTaskAssigneeCommand;
+import io.swagger.v3.oas.annotations.media.Schema;
+import jakarta.validation.constraints.Min;
+import jakarta.validation.constraints.NotNull;
+import java.util.UUID;
+
+@JsonNaming(PropertyNamingStrategies.SnakeCaseStrategy.class)
+public record ChangeTaskAssigneeRequest(
+        @Schema(
+                description = "같은 사업장의 활성 ADMIN 또는 HR 사용자 ID",
+                example = "7e2722bb-3c72-4aa0-b37c-28931c4f8e53"
+        )
+        @NotNull UUID assigneeId,
+        @Schema(description = "조회한 업무카드의 현재 version", example = "3")
+        @NotNull @Min(0) Long expectedVersion
+) {
+    ChangeTaskAssigneeCommand toCommand() {
+        return new ChangeTaskAssigneeCommand(assigneeId, expectedVersion);
+    }
+}
diff --git a/src/main/java/com/fowoco/server/task/api/TaskAssigneeResponse.java b/src/main/java/com/fowoco/server/task/api/TaskAssigneeResponse.java
new file mode 100644
index 0000000..1d88471
--- /dev/null
+++ b/src/main/java/com/fowoco/server/task/api/TaskAssigneeResponse.java
@@ -0,0 +1,17 @@
+package com.fowoco.server.task.api;
+
+import com.fasterxml.jackson.databind.PropertyNamingStrategies;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
+import com.fowoco.server.task.application.TaskAssigneeView;
+import io.swagger.v3.oas.annotations.media.Schema;
+import java.util.UUID;
+
+@JsonNaming(PropertyNamingStrategies.SnakeCaseStrategy.class)
+public record TaskAssigneeResponse(
+        @Schema(description = "담당자 사용자 ID") UUID userId,
+        @Schema(description = "화면에 표시할 담당자 이름") String displayName
+) {
+    public static TaskAssigneeResponse from(TaskAssigneeView assignee) {
+        return new TaskAssigneeResponse(assignee.userId(), assignee.displayName());
+    }
+}
diff --git a/src/main/java/com/fowoco/server/task/api/TaskController.java b/src/main/java/com/fowoco/server/task/api/TaskController.java
index b208353..41c35d6 100644
--- a/src/main/java/com/fowoco/server/task/api/TaskController.java
+++ b/src/main/java/com/fowoco/server/task/api/TaskController.java
@@ -159,6 +159,38 @@ public TaskDetailResponse update(
         ));
     }
 
+    @Operation(
+            operationId = "changeTaskAssignee",
+            summary = "업무카드 담당자 변경",
+            description = "같은 사업장의 활성 HR 또는 관리자를 담당자로 지정합니다."
+    )
+    @ApiResponses({
+            @ApiResponse(responseCode = "200", description = "담당자가 변경된 업무카드"),
+            @ApiResponse(responseCode = "400", ref = "#/components/responses/BadRequest"),
+            @ApiResponse(responseCode = "403", ref = "#/components/responses/Forbidden"),
+            @ApiResponse(responseCode = "404", ref = "#/components/responses/NotFound"),
+            @ApiResponse(responseCode = "409", ref = "#/components/responses/Conflict"),
+            @ApiResponse(responseCode = "422", ref = "#/components/responses/UnprocessableEntity")
+    })
+    @PreAuthorize("hasAnyRole('ADMIN', 'HR')")
+    @PatchMapping(
+            path = "/{taskId}/assignee",
+            consumes = MediaType.APPLICATION_JSON_VALUE,
+            produces = MediaType.APPLICATION_JSON_VALUE
+    )
+    public TaskDetailResponse changeAssignee(
+            @PathVariable UUID taskId,
+            @Valid @RequestBody ChangeTaskAssigneeRequest request,
+            HttpServletRequest servletRequest
+    ) {
+        return TaskDetailResponse.from(taskService.changeAssignee(
+                taskId,
+                request.toCommand(),
+                actor(),
+                RequestMetadata.from(servletRequest)
+        ));
+    }
+
     @Operation(operationId = "updateTaskChecklistItem", summary = "체크리스트 항목 수정")
     @ApiResponses({
             @ApiResponse(responseCode = "200", description = "체크리스트와 재평가된 업무 상태"),
diff --git a/src/main/java/com/fowoco/server/task/api/TaskDetailResponse.java b/src/main/java/com/fowoco/server/task/api/TaskDetailResponse.java
index b05e250..2fd67f7 100644
--- a/src/main/java/com/fowoco/server/task/api/TaskDetailResponse.java
+++ b/src/main/java/com/fowoco/server/task/api/TaskDetailResponse.java
@@ -29,6 +29,7 @@ public record TaskDetailResponse(
         TaskSource source,
         TaskStatus status,
         LocalDate dueDate,
+        TaskAssigneeResponse assignee,
         long contentRevision,
         long version,
         List<String> missingRequiredSlots,
@@ -54,6 +55,7 @@ static TaskDetailResponse from(TaskResult result) {
                 task.source(),
                 task.status(),
                 task.dueDate(),
+                TaskAssigneeResponse.from(result.assignee()),
                 task.contentRevision(),
                 task.version(),
                 result.missingRequiredSlots(),
diff --git a/src/main/java/com/fowoco/server/task/application/ChangeTaskAssigneeCommand.java b/src/main/java/com/fowoco/server/task/application/ChangeTaskAssigneeCommand.java
new file mode 100644
index 0000000..ac470e7
--- /dev/null
+++ b/src/main/java/com/fowoco/server/task/application/ChangeTaskAssigneeCommand.java
@@ -0,0 +1,16 @@
+package com.fowoco.server.task.application;
+
+import java.util.Objects;
+import java.util.UUID;
+
+public record ChangeTaskAssigneeCommand(
+        UUID assigneeId,
+        long expectedVersion
+) {
+    public ChangeTaskAssigneeCommand {
+        Objects.requireNonNull(assigneeId, "assigneeId must not be null");
+        if (expectedVersion < 0) {
+            throw new IllegalArgumentException("expectedVersion must not be negative");
+        }
+    }
+}
diff --git a/src/main/java/com/fowoco/server/task/application/TaskAssigneeView.java b/src/main/java/com/fowoco/server/task/application/TaskAssigneeView.java
new file mode 100644
index 0000000..23e5e6a
--- /dev/null
+++ b/src/main/java/com/fowoco/server/task/application/TaskAssigneeView.java
@@ -0,0 +1,17 @@
+package com.fowoco.server.task.application;
+
+import java.util.Objects;
+import java.util.UUID;
+
+public record TaskAssigneeView(
+        UUID userId,
+        String displayName
+) {
+    public TaskAssigneeView {
+        Objects.requireNonNull(userId, "userId must not be null");
+        if (displayName == null || displayName.isBlank()) {
+            throw new IllegalArgumentException("displayName must not be blank");
+        }
+        displayName = displayName.strip();
+    }
+}
diff --git a/src/main/java/com/fowoco/server/task/application/TaskResult.java b/src/main/java/com/fowoco/server/task/application/TaskResult.java
index a21be9e..faea9f4 100644
--- a/src/main/java/com/fowoco/server/task/application/TaskResult.java
+++ b/src/main/java/com/fowoco/server/task/application/TaskResult.java
@@ -9,6 +9,7 @@
 
 public record TaskResult(
         Task task,
+        TaskAssigneeView assignee,
         Map<String, Object> businessData,
         List<TaskChecklistItem> checklistItems,
         List<String> missingRequiredSlots
diff --git a/src/main/java/com/fowoco/server/task/application/TaskWorkflowService.java b/src/main/java/com/fowoco/server/task/application/TaskWorkflowService.java
index 96e7bd4..cfccfe5 100644
--- a/src/main/java/com/fowoco/server/task/application/TaskWorkflowService.java
+++ b/src/main/java/com/fowoco/server/task/application/TaskWorkflowService.java
@@ -8,6 +8,8 @@
 import com.fowoco.server.audit.domain.AuditTargetType;
 import com.fowoco.server.auth.application.ActorAuthorizer;
 import com.fowoco.server.auth.application.ActorContext;
+import com.fowoco.server.auth.application.CompanyMemberAccount;
+import com.fowoco.server.auth.application.port.CompanyMemberDirectory;
 import com.fowoco.server.auth.domain.UserRole;
 import com.fowoco.server.common.error.ApiException;
 import com.fowoco.server.common.id.UuidGenerator;
@@ -48,6 +50,7 @@ public class TaskWorkflowService {
 
     private static final String AUDIT_EVENT_VERSION = "1";
     private final ActorAuthorizer actorAuthorizer;
+    private final CompanyMemberDirectory companyMemberDirectory;
     private final TenantDatabaseContext tenantDatabaseContext;
     private final TaskRepository taskRepository;
     private final TaskChecklistRepository checklistRepository;
@@ -64,6 +67,7 @@ public class TaskWorkflowService {
 
     public TaskWorkflowService(
             ActorAuthorizer actorAuthorizer,
+            CompanyMemberDirectory companyMemberDirectory,
             TenantDatabaseContext tenantDatabaseContext,
             TaskRepository taskRepository,
             TaskChecklistRepository checklistRepository,
@@ -79,6 +83,7 @@ public TaskWorkflowService(
             Clock clock
     ) {
         this.actorAuthorizer = actorAuthorizer;
+        this.companyMemberDirectory = companyMemberDirectory;
         this.tenantDatabaseContext = tenantDatabaseContext;
         this.taskRepository = taskRepository;
         this.checklistRepository = checklistRepository;
@@ -333,6 +338,51 @@ public TaskResult update(
         );
     }
 
+    @Transactional
+    public TaskResult changeAssignee(
+            UUID taskId,
+            ChangeTaskAssigneeCommand command,
+            ActorContext actor,
+            RequestMetadata metadata
+    ) {
+        bindTenant(actor);
+        actorAuthorizer.requireHrWrite(actor);
+        Task task = requireTask(taskId, actor.companyId());
+        TaskAssigneeView nextAssignee = requireAssignableAssignee(
+                actor.companyId(),
+                command.assigneeId()
+        );
+        UUID previousAssigneeId = task.assigneeId();
+        Instant now = Instant.now(clock);
+        boolean changed = task.changeAssignee(
+                command.assigneeId(),
+                command.expectedVersion(),
+                actor.actorId(),
+                now
+        );
+        Task savedTask = changed ? taskRepository.save(task) : task;
+        if (changed) {
+            appendAudit(
+                    savedTask,
+                    actor,
+                    AuditAction.TASK_ASSIGNEE_CHANGED,
+                    "업무 담당자를 변경함 (%s → %s)".formatted(
+                            previousAssigneeId,
+                            savedTask.assigneeId()
+                    ),
+                    metadata,
+                    now
+            );
+        }
+        return toResult(
+                savedTask,
+                checklistRepository.findAllByTaskIdAndCompanyId(taskId, actor.companyId()),
+                findWorker(savedTask, actor.companyId()),
+                catalogService.requireWorkflow(savedTask.workflowId()),
+                nextAssignee
+        );
+    }
+
     @Transactional
     public TaskResult updateChecklistItem(
             UUID taskId,
@@ -469,16 +519,57 @@ private TaskResult toResult(
             List<TaskChecklistItem> checklistItems,
             WorkerTaskContext worker,
             WorkflowDefinition workflow
+    ) {
+        return toResult(
+                task,
+                checklistItems,
+                worker,
+                workflow,
+                requireAssignee(task, task.companyId())
+        );
+    }
+
+    private TaskResult toResult(
+            Task task,
+            List<TaskChecklistItem> checklistItems,
+            WorkerTaskContext worker,
+            WorkflowDefinition workflow,
+            TaskAssigneeView assignee
     ) {
         Map<String, Object> businessData = contentCodec.decodeBusinessData(task.businessDataJson());
         return new TaskResult(
                 task,
+                assignee,
                 businessData,
                 checklistItems,
                 missingRequiredSlots(workflow, worker, task.dueDate(), businessData)
         );
     }
 
+    private TaskAssigneeView requireAssignableAssignee(UUID companyId, UUID assigneeId) {
+        CompanyMemberAccount member = requireCompanyMember(companyId, assigneeId);
+        boolean assignableRole = member.role() == UserRole.ADMIN || member.role() == UserRole.HR;
+        if (!member.active() || !assignableRole) {
+            throw new ApiException(TaskErrorCode.TASK_ASSIGNEE_NOT_ASSIGNABLE);
+        }
+        return toAssigneeView(member);
+    }
+
+    private TaskAssigneeView requireAssignee(Task task, UUID companyId) {
+        return toAssigneeView(requireCompanyMember(companyId, task.assigneeId()));
+    }
+
+    private CompanyMemberAccount requireCompanyMember(UUID companyId, UUID userId) {
+        return companyMemberDirectory.findByCompanyId(companyId, null, false).stream()
+                .filter(member -> member.userId().equals(userId))
+                .findFirst()
+                .orElseThrow(() -> new ApiException(TaskErrorCode.TASK_ASSIGNEE_NOT_FOUND));
+    }
+
+    private TaskAssigneeView toAssigneeView(CompanyMemberAccount member) {
+        return new TaskAssigneeView(member.userId(), member.displayName());
+    }
+
     private List<String> missingRequiredSlots(
             WorkflowDefinition workflow,
             WorkerTaskContext worker,
diff --git a/src/main/java/com/fowoco/server/task/application/error/TaskErrorCode.java b/src/main/java/com/fowoco/server/task/application/error/TaskErrorCode.java
index 51f8fe9..55d2f4a 100644
--- a/src/main/java/com/fowoco/server/task/application/error/TaskErrorCode.java
+++ b/src/main/java/com/fowoco/server/task/application/error/TaskErrorCode.java
@@ -5,6 +5,11 @@
 
 public enum TaskErrorCode implements ApiErrorCode {
     TASK_NOT_FOUND(HttpStatus.NOT_FOUND, "업무카드를 찾을 수 없습니다."),
+    TASK_ASSIGNEE_NOT_FOUND(HttpStatus.NOT_FOUND, "지정할 담당자를 찾을 수 없습니다."),
+    TASK_ASSIGNEE_NOT_ASSIGNABLE(
+            HttpStatus.UNPROCESSABLE_CONTENT,
+            "활성 상태의 HR 또는 관리자만 업무 담당자로 지정할 수 있습니다."
+    ),
     WORKER_NOT_FOUND(HttpStatus.NOT_FOUND, "근로자를 찾을 수 없습니다."),
     WORKFLOW_NOT_FOUND(HttpStatus.NOT_FOUND, "Workflow를 찾을 수 없습니다."),
     WORKFLOW_TASK_TYPE_MISMATCH(
diff --git a/src/main/java/com/fowoco/server/task/domain/Task.java b/src/main/java/com/fowoco/server/task/domain/Task.java
index 45cd8dc..87c6da8 100644
--- a/src/main/java/com/fowoco/server/task/domain/Task.java
+++ b/src/main/java/com/fowoco/server/task/domain/Task.java
@@ -25,6 +25,7 @@ public final class Task {
     private final TaskSource source;
     private TaskStatus status;
     private LocalDate dueDate;
+    private UUID assigneeId;
     private final UUID createdBy;
     private UUID updatedBy;
     private final Instant createdAt;
@@ -48,6 +49,7 @@ public Task(
             TaskSource source,
             TaskStatus status,
             LocalDate dueDate,
+            UUID assigneeId,
             UUID createdBy,
             UUID updatedBy,
             Instant createdAt,
@@ -74,6 +76,7 @@ public Task(
         this.source = Objects.requireNonNull(source);
         this.status = Objects.requireNonNull(status);
         this.dueDate = dueDate;
+        this.assigneeId = Objects.requireNonNull(assigneeId);
         this.createdBy = Objects.requireNonNull(createdBy);
         this.updatedBy = Objects.requireNonNull(updatedBy);
         this.createdAt = Objects.requireNonNull(createdAt);
@@ -121,6 +124,7 @@ public Task(
                 status,
                 dueDate,
                 createdBy,
+                createdBy,
                 updatedBy,
                 createdAt,
                 updatedAt,
@@ -169,6 +173,7 @@ public static Task create(
                 dueDate,
                 actorId,
                 actorId,
+                actorId,
                 now,
                 now,
                 0
@@ -287,6 +292,26 @@ public TaskStatus cancel(long expectedVersion, UUID actorId, Instant now) {
         return transition(TaskStatus.CANCELLED, actorId, now);
     }
 
+    public boolean changeAssignee(
+            UUID assigneeId,
+            long expectedVersion,
+            UUID actorId,
+            Instant now
+    ) {
+        requireVersion(expectedVersion);
+        if (status.isTerminal()) {
+            throw new ApiException(TaskErrorCode.TASK_TRANSITION_NOT_ALLOWED);
+        }
+        UUID nextAssigneeId = Objects.requireNonNull(assigneeId);
+        if (this.assigneeId.equals(nextAssigneeId)) {
+            return false;
+        }
+        this.assigneeId = nextAssigneeId;
+        this.updatedBy = Objects.requireNonNull(actorId);
+        this.updatedAt = Objects.requireNonNull(now);
+        return true;
+    }
+
     public UpdateOutcome updateContent(
             String title,
             String description,
@@ -481,6 +506,10 @@ public LocalDate dueDate() {
         return dueDate;
     }
 
+    public UUID assigneeId() {
+        return assigneeId;
+    }
+
     public UUID createdBy() {
         return createdBy;
     }
diff --git a/src/main/java/com/fowoco/server/task/infrastructure/persistence/TaskJpaEntity.java b/src/main/java/com/fowoco/server/task/infrastructure/persistence/TaskJpaEntity.java
index 560c69e..849e623 100644
--- a/src/main/java/com/fowoco/server/task/infrastructure/persistence/TaskJpaEntity.java
+++ b/src/main/java/com/fowoco/server/task/infrastructure/persistence/TaskJpaEntity.java
@@ -64,6 +64,8 @@ public class TaskJpaEntity {
     private TaskStatus status;
     @Column(name = "due_date")
     private LocalDate dueDate;
+    @Column(name = "assignee_id")
+    private UUID assigneeId;
     @Column(name = "created_by", nullable = false, updatable = false)
     private UUID createdBy;
     @Column(name = "updated_by", nullable = false)
@@ -92,6 +94,7 @@ public void apply(Task task) {
         this.contentRevision = task.contentRevision();
         this.status = task.status();
         this.dueDate = task.dueDate();
+        this.assigneeId = task.assigneeId();
         this.updatedBy = task.updatedBy();
         this.updatedAt = task.updatedAt();
     }
@@ -113,6 +116,7 @@ private void copyFrom(Task task) {
         this.source = task.source();
         this.status = task.status();
         this.dueDate = task.dueDate();
+        this.assigneeId = task.assigneeId();
         this.createdBy = task.createdBy();
         this.updatedBy = task.updatedBy();
         this.createdAt = task.createdAt();
@@ -137,6 +141,7 @@ public Task toDomain() {
                 source,
                 status,
                 dueDate,
+                assigneeId == null ? createdBy : assigneeId,
                 createdBy,
                 updatedBy,
                 createdAt,
diff --git a/src/main/resources/db/migration/V42__add_task_assignee.sql b/src/main/resources/db/migration/V42__add_task_assignee.sql
new file mode 100644
index 0000000..1f7f8fe
--- /dev/null
+++ b/src/main/resources/db/migration/V42__add_task_assignee.sql
@@ -0,0 +1,14 @@
+ALTER TABLE task
+    ADD COLUMN assignee_id UUID;
+
+UPDATE task
+SET assignee_id = created_by
+WHERE assignee_id IS NULL;
+
+ALTER TABLE task
+    ADD CONSTRAINT fk_task_assignee_company
+        FOREIGN KEY (assignee_id, company_id)
+        REFERENCES user_account (user_id, company_id) ON DELETE RESTRICT;
+
+CREATE INDEX idx_task_company_assignee
+    ON task (company_id, assignee_id);
diff --git a/src/test/java/com/fowoco/server/task/TaskWorkflowIntegrationTest.java b/src/test/java/com/fowoco/server/task/TaskWorkflowIntegrationTest.java
index 0a9d9cf..b279a5b 100644
--- a/src/test/java/com/fowoco/server/task/TaskWorkflowIntegrationTest.java
+++ b/src/test/java/com/fowoco/server/task/TaskWorkflowIntegrationTest.java
@@ -1,6 +1,7 @@
 package com.fowoco.server.task;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 import com.jayway.jsonpath.JsonPath;
 import java.net.URI;
@@ -22,6 +23,7 @@
 import org.springframework.boot.test.web.server.LocalServerPort;
 import org.springframework.http.HttpHeaders;
 import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.dao.DataIntegrityViolationException;
 import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.test.context.ActiveProfiles;
 
@@ -37,6 +39,10 @@ class TaskWorkflowIntegrationTest {
             UUID.fromString("c1000000-0000-0000-0000-000000000001");
     private static final UUID VIEWER_A =
             UUID.fromString("c2000000-0000-0000-0000-000000000001");
+    private static final UUID HR_A_SECOND =
+            UUID.fromString("c1000000-0000-0000-0000-000000000002");
+    private static final UUID SUSPENDED_HR_A =
+            UUID.fromString("c1000000-0000-0000-0000-000000000003");
     private static final UUID HR_B =
             UUID.fromString("d1000000-0000-0000-0000-000000000001");
     private static final UUID WORKER_A =
@@ -44,6 +50,7 @@ class TaskWorkflowIntegrationTest {
     private static final String PASSWORD = "Test-password-1!";
     private static final String HR_A_EMAIL = "task.hr.a@example.com";
     private static final String VIEWER_A_EMAIL = "task.viewer.a@example.com";
+    private static final String HR_A_SECOND_EMAIL = "task.hr.a.second@example.com";
     private static final String HR_B_EMAIL = "task.hr.b@example.com";
 
     @LocalServerPort
@@ -77,12 +84,122 @@ void resetAndSeed() {
         insertCompany(COMPANY_A, "Task 테스트 사업장 A");
         insertCompany(COMPANY_B, "Task 테스트 사업장 B");
         String passwordHash = passwordEncoder.encode(PASSWORD);
-        insertUser(HR_A, COMPANY_A, HR_A_EMAIL, passwordHash, "HR");
-        insertUser(VIEWER_A, COMPANY_A, VIEWER_A_EMAIL, passwordHash, "VIEWER");
-        insertUser(HR_B, COMPANY_B, HR_B_EMAIL, passwordHash, "HR");
+        insertUser(HR_A, COMPANY_A, HR_A_EMAIL, "담당자 A", passwordHash, "HR");
+        insertUser(HR_A_SECOND, COMPANY_A, HR_A_SECOND_EMAIL, "담당자 B", passwordHash, "HR");
+        insertUser(
+                SUSPENDED_HR_A,
+                COMPANY_A,
+                "task.hr.a.suspended@example.com",
+                "정지 담당자",
+                passwordHash,
+                "HR"
+        );
+        jdbcTemplate.update(
+                "UPDATE user_account SET status = 'SUSPENDED' WHERE user_id = ?",
+                SUSPENDED_HR_A
+        );
+        insertUser(VIEWER_A, COMPANY_A, VIEWER_A_EMAIL, "조회자 A", passwordHash, "VIEWER");
+        insertUser(HR_B, COMPANY_B, HR_B_EMAIL, "담당자 B사", passwordHash, "HR");
         insertWorker();
     }
 
+    @Test
+    void changesTaskAssigneeAndReturnsItFromTaskDetail() throws Exception {
+        String hrToken = login(HR_A_EMAIL);
+        HttpResponse<String> created = post("/api/v1/tasks", validCreateBody(), hrToken);
+        UUID taskId = UUID.fromString(JsonPath.read(created.body(), "$.task_id"));
+        assertThat(JsonPath.<String>read(created.body(), "$.assignee.user_id"))
+                .isEqualTo(HR_A.toString());
+        assertThat(JsonPath.<String>read(created.body(), "$.assignee.display_name"))
+                .isEqualTo("담당자 A");
+
+        HttpResponse<String> changed = patch(
+                "/api/v1/tasks/" + taskId + "/assignee",
+                """
+                {
+                  "assignee_id":"%s",
+                  "expected_version":0
+                }
+                """.formatted(HR_A_SECOND),
+                hrToken
+        );
+
+        assertThat(changed.statusCode()).isEqualTo(200);
+        assertThat(JsonPath.<String>read(changed.body(), "$.assignee.user_id"))
+                .isEqualTo(HR_A_SECOND.toString());
+        assertThat(JsonPath.<String>read(changed.body(), "$.assignee.display_name"))
+                .isEqualTo("담당자 B");
+        assertThat(JsonPath.<Number>read(changed.body(), "$.version").longValue()).isEqualTo(1);
+
+        HttpResponse<String> detail = get("/api/v1/tasks/" + taskId, hrToken);
+        assertThat(JsonPath.<String>read(detail.body(), "$.assignee.user_id"))
+                .isEqualTo(HR_A_SECOND.toString());
+        assertThat(jdbcTemplate.queryForObject(
+                "SELECT assignee_id FROM task WHERE task_id = ?",
+                UUID.class,
+                taskId
+        )).isEqualTo(HR_A_SECOND);
+        assertThat(jdbcTemplate.queryForObject(
+                "SELECT COUNT(*) FROM audit_event "
+                        + "WHERE target_id = ? AND action = 'TASK_ASSIGNEE_CHANGED'",
+                Integer.class,
+                taskId
+        )).isEqualTo(1);
+    }
+
+    @Test
+    void rejectsUnauthorizedCrossCompanyInactiveViewerAndStaleAssigneeChanges() throws Exception {
+        String hrToken = login(HR_A_EMAIL);
+        UUID taskId = UUID.fromString(JsonPath.read(
+                post("/api/v1/tasks", validCreateBody(), hrToken).body(),
+                "$.task_id"
+        ));
+        String request = """
+                {"assignee_id":"%s","expected_version":0}
+                """.formatted(HR_A_SECOND);
+        assertThat(patch("/api/v1/tasks/" + taskId + "/assignee", request, hrToken).statusCode())
+                .isEqualTo(200);
+
+        assertThat(patch(
+                "/api/v1/tasks/" + taskId + "/assignee",
+                request,
+                hrToken
+        ).statusCode()).isEqualTo(409);
+        assertThat(patch(
+                "/api/v1/tasks/" + taskId + "/assignee",
+                """
+                {"assignee_id":"%s","expected_version":1}
+                """.formatted(HR_B),
+                hrToken
+        ).statusCode()).isEqualTo(404);
+        assertThat(patch(
+                "/api/v1/tasks/" + taskId + "/assignee",
+                """
+                {"assignee_id":"%s","expected_version":1}
+                """.formatted(SUSPENDED_HR_A),
+                hrToken
+        ).statusCode()).isEqualTo(422);
+        assertThat(patch(
+                "/api/v1/tasks/" + taskId + "/assignee",
+                """
+                {"assignee_id":"%s","expected_version":1}
+                """.formatted(VIEWER_A),
+                hrToken
+        ).statusCode()).isEqualTo(422);
+        assertThat(patch(
+                "/api/v1/tasks/" + taskId + "/assignee",
+                """
+                {"assignee_id":"%s","expected_version":1}
+                """.formatted(HR_A),
+                login(VIEWER_A_EMAIL)
+        ).statusCode()).isEqualTo(403);
+        assertThatThrownBy(() -> jdbcTemplate.update(
+                "UPDATE task SET assignee_id = ? WHERE task_id = ?",
+                HR_B,
+                taskId
+        )).isInstanceOf(DataIntegrityViolationException.class);
+    }
+
     @Test
     void supportsTheCatalogTaskChecklistAndCancelApiFlow() throws Exception {
         String token = login(HR_A_EMAIL);
@@ -694,18 +811,20 @@ private void insertUser(
             UUID userId,
             UUID companyId,
             String email,
+            String displayName,
             String passwordHash,
             String role
     ) {
         jdbcTemplate.update(
                 """
                 INSERT INTO user_account (
-                    user_id, company_id, email, normalized_email, password_hash,
+                    user_id, company_id, display_name, email, normalized_email, password_hash,
                     role, status, created_at, updated_at, version
-                ) VALUES (?, ?, ?, ?, ?, ?, 'ACTIVE', CURRENT_TIMESTAMP, CURRENT_TIMESTAMP, 0)
+                ) VALUES (?, ?, ?, ?, ?, ?, ?, 'ACTIVE', CURRENT_TIMESTAMP, CURRENT_TIMESTAMP, 0)
                 """,
                 userId,
                 companyId,
+                displayName,
                 email,
                 email,
                 passwordHash,
diff --git a/src/test/java/com/fowoco/server/task/domain/TaskTest.java b/src/test/java/com/fowoco/server/task/domain/TaskTest.java
index c6393eb..da5af06 100644
--- a/src/test/java/com/fowoco/server/task/domain/TaskTest.java
+++ b/src/test/java/com/fowoco/server/task/domain/TaskTest.java
@@ -101,6 +101,38 @@ void rejectsAStaleExpectedVersion() {
                         assertThat(exception.errorCode()).isEqualTo(TaskErrorCode.CONCURRENT_MODIFICATION));
     }
 
+    @Test
+    void changesAssigneeWithoutChangingTaskContentOrStatus() {
+        Task task = task(TaskStatus.APPROVED);
+        UUID nextAssigneeId = UUID.fromString("10000000-0000-0000-0000-000000000002");
+
+        boolean changed = task.changeAssignee(
+                nextAssigneeId,
+                0,
+                ACTOR_ID,
+                NOW.plusSeconds(1)
+        );
+
+        assertThat(changed).isTrue();
+        assertThat(task.assigneeId()).isEqualTo(nextAssigneeId);
+        assertThat(task.status()).isEqualTo(TaskStatus.APPROVED);
+        assertThat(task.contentRevision()).isZero();
+    }
+
+    @Test
+    void terminalTaskRejectsAssigneeChange() {
+        Task task = task(TaskStatus.COMPLETED);
+
+        assertThatThrownBy(() -> task.changeAssignee(
+                UUID.randomUUID(),
+                0,
+                ACTOR_ID,
+                NOW.plusSeconds(1)
+        )).isInstanceOfSatisfying(ApiException.class, exception ->
+                assertThat(exception.errorCode())
+                        .isEqualTo(TaskErrorCode.TASK_TRANSITION_NOT_ALLOWED));
+    }
+
     @Test
     void terminalTaskCannotBeCancelledAgain() {
         Task task = task(TaskStatus.COMPLETED);