diff --git a/dictation_server/src/repositories/worktypes/worktypes.repository.service.ts b/dictation_server/src/repositories/worktypes/worktypes.repository.service.ts
index f647288..07e1704 100644
--- a/dictation_server/src/repositories/worktypes/worktypes.repository.service.ts
+++ b/dictation_server/src/repositories/worktypes/worktypes.repository.service.ts
@@ -88,6 +88,7 @@ export class WorktypesRepositoryService {
       const duplicatedWorktype = await worktypeRepo.findOne({
         where: { account_id: accountId, custom_worktype_id: worktypeId },
         comment: `${context.getTrackingId()}_${new Date().toUTCString()}`,
+        lock: { mode: 'pessimistic_write' },
       });
 
       // ワークタイプIDが重複している場合はエラー
@@ -100,6 +101,7 @@ export class WorktypesRepositoryService {
       const worktypeCount = await worktypeRepo.count({
         where: { account_id: accountId },
         comment: `${context.getTrackingId()}_${new Date().toUTCString()}`,
+        lock: { mode: 'pessimistic_write' },
       });
 
       // ワークタイプの登録数が上限に達している場合はエラー
@@ -163,6 +165,7 @@ export class WorktypesRepositoryService {
       const worktype = await worktypeRepo.findOne({
         where: { account_id: accountId, id: id },
         comment: `${context.getTrackingId()}_${new Date().toUTCString()}`,
+        lock: { mode: 'pessimistic_write' },
       });
 
       // ワークタイプが存在しない場合はエラー
@@ -177,6 +180,7 @@ export class WorktypesRepositoryService {
           id: Not(id),
         },
         comment: `${context.getTrackingId()}_${new Date().toUTCString()}`,
+        lock: { mode: 'pessimistic_write' },
       });
 
       // ワークタイプIDが重複している場合はエラー
@@ -227,6 +231,7 @@ export class WorktypesRepositoryService {
       const account = await accountRepo.findOne({
         where: { id: accountId },
         comment: `${context.getTrackingId()}_${new Date().toUTCString()}`,
+        lock: { mode: 'pessimistic_write' },
       });
 
       if (account?.active_worktype_id === id) {
@@ -244,6 +249,7 @@ export class WorktypesRepositoryService {
       const workflows = await workflowRepo.find({
         where: { account_id: accountId, worktype_id: id },
         comment: `${context.getTrackingId()}_${new Date().toUTCString()}`,
+        lock: { mode: 'pessimistic_write' },
       });
       if (workflows.length > 0) {
         const workflowIds = workflows.map((workflow) => workflow.id);
@@ -322,6 +328,7 @@ export class WorktypesRepositoryService {
       const worktype = await worktypeRepo.findOne({
         where: { account_id: accountId, id: worktypeId },
         comment: `${context.getTrackingId()}_${new Date().toUTCString()}`,
+        lock: { mode: 'pessimistic_write' },
       });
       // ワークタイプが存在しない場合はエラー
       if (!worktype) {