diff --git a/apps/app/package.json b/apps/app/package.json
index 03e6363742e..2524145964a 100644
--- a/apps/app/package.json
+++ b/apps/app/package.json
@@ -235,6 +235,7 @@
     "@testing-library/user-event": "^14.5.2",
     "@types/express": "^4.17.21",
     "@types/jest": "^29.5.2",
+    "@types/node-cron": "^3.0.11",
     "@types/react-input-autosize": "^2.2.4",
     "@types/react-scroll": "^1.8.4",
     "@types/react-stickynode": "^4.0.3",
@@ -275,8 +276,8 @@
     "react-hotkeys": "^2.0.0",
     "react-input-autosize": "^3.0.0",
     "react-toastify": "^9.1.3",
-    "remark-github-admonitions-to-directives": "^2.0.0",
     "rehype-rewrite": "^4.0.2",
+    "remark-github-admonitions-to-directives": "^2.0.0",
     "replacestream": "^4.0.3",
     "sass": "^1.53.0",
     "simple-load-script": "^1.0.2",
diff --git a/apps/app/src/features/openai/server/models/thread-relation.ts b/apps/app/src/features/openai/server/models/thread-relation.ts
index 736a1c0c616..e333545f5f9 100644
--- a/apps/app/src/features/openai/server/models/thread-relation.ts
+++ b/apps/app/src/features/openai/server/models/thread-relation.ts
@@ -21,7 +21,9 @@ interface ThreadRelationDocument extends ThreadRelation, Document {
   updateThreadExpiration(): Promise<void>;
 }
 
-type ThreadRelationModel = Model<ThreadRelationDocument>
+interface ThreadRelationModel extends Model<ThreadRelationDocument> {
+  getExpiredThreadRelations(limit?: number): Promise<ThreadRelationDocument[] | undefined>;
+}
 
 const schema = new Schema<ThreadRelationDocument, ThreadRelationModel>({
   userId: {
@@ -41,6 +43,12 @@ const schema = new Schema<ThreadRelationDocument, ThreadRelationModel>({
   },
 });
 
+schema.statics.getExpiredThreadRelations = async function(limit?: number): Promise<ThreadRelationDocument[] | undefined> {
+  const currentDate = new Date();
+  const expiredThreadRelations = await this.find({ expiredAt: { $lte: currentDate } }).limit(limit ?? 100).exec();
+  return expiredThreadRelations;
+};
+
 schema.methods.updateThreadExpiration = async function(): Promise<void> {
   this.expiredAt = generateExpirationDate();
   await this.save();
diff --git a/apps/app/src/features/openai/server/services/client-delegator/azure-openai-client-delegator.ts b/apps/app/src/features/openai/server/services/client-delegator/azure-openai-client-delegator.ts
index 202d1be517b..63c0d3237fd 100644
--- a/apps/app/src/features/openai/server/services/client-delegator/azure-openai-client-delegator.ts
+++ b/apps/app/src/features/openai/server/services/client-delegator/azure-openai-client-delegator.ts
@@ -36,6 +36,10 @@ export class AzureOpenaiClientDelegator implements IOpenaiClientDelegator {
     return this.client.beta.threads.retrieve(threadId);
   }
 
+  async deleteThread(threadId: string): Promise<OpenAI.Beta.Threads.ThreadDeleted> {
+    return this.client.beta.threads.del(threadId);
+  }
+
   async createVectorStore(scopeType:VectorStoreScopeType): Promise<OpenAI.Beta.VectorStores.VectorStore> {
     return this.client.beta.vectorStores.create({ name: `growi-vector-store-{${scopeType}` });
   }
diff --git a/apps/app/src/features/openai/server/services/client-delegator/interfaces.ts b/apps/app/src/features/openai/server/services/client-delegator/interfaces.ts
index 01e9df8af89..e2f2f6dcd8e 100644
--- a/apps/app/src/features/openai/server/services/client-delegator/interfaces.ts
+++ b/apps/app/src/features/openai/server/services/client-delegator/interfaces.ts
@@ -6,6 +6,7 @@ import type { VectorStoreScopeType } from '~/features/openai/server/models/vecto
 export interface IOpenaiClientDelegator {
   createThread(vectorStoreId: string): Promise<OpenAI.Beta.Threads.Thread>
   retrieveThread(threadId: string): Promise<OpenAI.Beta.Threads.Thread>
+  deleteThread(threadId: string): Promise<OpenAI.Beta.Threads.ThreadDeleted>
   retrieveVectorStore(vectorStoreId: string): Promise<OpenAI.Beta.VectorStores.VectorStore>
   createVectorStore(scopeType:VectorStoreScopeType): Promise<OpenAI.Beta.VectorStores.VectorStore>
   uploadFile(file: Uploadable): Promise<OpenAI.Files.FileObject>
diff --git a/apps/app/src/features/openai/server/services/client-delegator/openai-client-delegator.ts b/apps/app/src/features/openai/server/services/client-delegator/openai-client-delegator.ts
index 9c8c3e2b664..8a54ac9a565 100644
--- a/apps/app/src/features/openai/server/services/client-delegator/openai-client-delegator.ts
+++ b/apps/app/src/features/openai/server/services/client-delegator/openai-client-delegator.ts
@@ -38,6 +38,10 @@ export class OpenaiClientDelegator implements IOpenaiClientDelegator {
     return this.client.beta.threads.retrieve(threadId);
   }
 
+  async deleteThread(threadId: string): Promise<OpenAI.Beta.Threads.ThreadDeleted> {
+    return this.client.beta.threads.del(threadId);
+  }
+
   async createVectorStore(scopeType:VectorStoreScopeType): Promise<OpenAI.Beta.VectorStores.VectorStore> {
     return this.client.beta.vectorStores.create({ name: `growi-vector-store-${scopeType}` });
   }
diff --git a/apps/app/src/features/openai/server/services/openai.ts b/apps/app/src/features/openai/server/services/openai.ts
index 8cb0f82b7a8..cf36aee39f8 100644
--- a/apps/app/src/features/openai/server/services/openai.ts
+++ b/apps/app/src/features/openai/server/services/openai.ts
@@ -32,6 +32,7 @@ let isVectorStoreForPublicScopeExist = false;
 export interface IOpenaiService {
   getOrCreateThread(userId: string, vectorStoreId?: string, threadId?: string): Promise<OpenAI.Beta.Threads.Thread | undefined>;
   getOrCreateVectorStoreForPublicScope(): Promise<VectorStoreDocument>;
+  deleteExpiredThreads(limit: number): Promise<void>;
   createVectorStoreFile(pages: PageDocument[]): Promise<void>;
   deleteVectorStoreFile(pageId: Types.ObjectId): Promise<void>;
   rebuildVectorStoreAll(): Promise<void>;
@@ -70,6 +71,28 @@ class OpenaiService implements IOpenaiService {
     return thread;
   }
 
+  public async deleteExpiredThreads(limit: number): Promise<void> {
+    const expiredThreadRelations = await ThreadRelationModel.getExpiredThreadRelations(limit);
+    if (expiredThreadRelations == null) {
+      return;
+    }
+
+    const deletedThreadIds: string[] = [];
+    for (const expiredThreadRelation of expiredThreadRelations) {
+      try {
+        // eslint-disable-next-line no-await-in-loop
+        const deleteThreadResponse = await this.client.deleteThread(expiredThreadRelation.threadId);
+        logger.debug('Delete thread', deleteThreadResponse);
+        deletedThreadIds.push(expiredThreadRelation.threadId);
+      }
+      catch (err) {
+        logger.error(err);
+      }
+    }
+
+    await ThreadRelationModel.deleteMany({ threadId: { $in: deletedThreadIds } });
+  }
+
   public async getOrCreateVectorStoreForPublicScope(): Promise<VectorStoreDocument> {
     const vectorStoreDocument = await VectorStoreModel.findOne({ scorpeType: VectorStoreScopeType.PUBLIC });
 
diff --git a/apps/app/src/features/openai/server/services/thread-deletion-cron.ts b/apps/app/src/features/openai/server/services/thread-deletion-cron.ts
new file mode 100644
index 00000000000..226e85783e5
--- /dev/null
+++ b/apps/app/src/features/openai/server/services/thread-deletion-cron.ts
@@ -0,0 +1,59 @@
+import nodeCron from 'node-cron';
+
+import { configManager } from '~/server/service/config-manager';
+import loggerFactory from '~/utils/logger';
+
+import { getOpenaiService, type IOpenaiService } from './openai';
+
+
+const logger = loggerFactory('growi:service:thread-deletion-cron');
+
+const DELETE_LIMIT = 100;
+
+class ThreadDeletionCronService {
+
+  cronJob: nodeCron.ScheduledTask;
+
+  openaiService: IOpenaiService;
+
+  startCron(): void {
+    const isAiEnabled = configManager.getConfig('crowi', 'app:aiEnabled');
+    if (!isAiEnabled) {
+      return;
+    }
+
+    const openaiService = getOpenaiService();
+    if (openaiService == null) {
+      throw new Error('OpenAI service is not initialized');
+    }
+
+    this.openaiService = openaiService;
+
+    // Executed at 0 minutes of every hour
+    const cronSchedule = '0 * * * *';
+
+    this.cronJob?.stop();
+    this.cronJob = this.generateCronJob(cronSchedule);
+    this.cronJob.start();
+  }
+
+  private async executeJob(): Promise<void> {
+    // Must be careful of OpenAI's rate limit
+    // Delete up to 100 threads per hour
+    await this.openaiService.deleteExpiredThreads(DELETE_LIMIT);
+  }
+
+  private generateCronJob(cronSchedule: string) {
+    return nodeCron.schedule(cronSchedule, async() => {
+      try {
+        await this.executeJob();
+      }
+      catch (e) {
+        logger.error(e);
+      }
+    });
+  }
+
+}
+
+export default ThreadDeletionCronService;
diff --git a/apps/app/src/server/crowi/index.js b/apps/app/src/server/crowi/index.js
index f3fccaa3fbe..9c7aec8fa1f 100644
--- a/apps/app/src/server/crowi/index.js
+++ b/apps/app/src/server/crowi/index.js
@@ -12,6 +12,7 @@ import pkg from '^/package.json';
 
 import { KeycloakUserGroupSyncService } from '~/features/external-user-group/server/service/keycloak-user-group-sync';
 import { LdapUserGroupSyncService } from '~/features/external-user-group/server/service/ldap-user-group-sync';
+import OpenaiThreadDeletionCronService from '~/features/openai/server/services/thread-deletion-cron';
 import QuestionnaireService from '~/features/questionnaire/server/service/questionnaire';
 import QuestionnaireCronService from '~/features/questionnaire/server/service/questionnaire-cron';
 import loggerFactory from '~/utils/logger';
@@ -102,6 +103,7 @@ class Crowi {
     this.commentService = null;
     this.questionnaireService = null;
     this.questionnaireCronService = null;
+    this.openaiThreadDeletionCronService = null;
 
     this.tokens = null;
 
@@ -312,6 +314,9 @@ Crowi.prototype.setupSocketIoService = async function() {
 Crowi.prototype.setupCron = function() {
   this.questionnaireCronService = new QuestionnaireCronService(this);
   this.questionnaireCronService.startCron();
+
+  this.openaiThreadDeletionCronService = new OpenaiThreadDeletionCronService();
+  this.openaiThreadDeletionCronService.startCron();
 };
 
 Crowi.prototype.setupQuestionnaireService = function() {
diff --git a/yarn.lock b/yarn.lock
index 58bb54b89b7..bc47ad2440b 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -4687,6 +4687,11 @@
   resolved "https://registry.yarnpkg.com/@types/ms/-/ms-0.7.31.tgz#31b7ca6407128a3d2bbc27fe2d21b345397f6197"
   integrity sha512-iiUgKzV9AuaEkZqkOLDIvlQiL6ltuZd9tGcW3gwpnX8JbuiuhFlEGmmFXEXkN50Cvq7Os88IY2v0dkDqXYWVgA==
 
+"@types/node-cron@^3.0.11":
+  version "3.0.11"
+  resolved "https://registry.yarnpkg.com/@types/node-cron/-/node-cron-3.0.11.tgz#70b7131f65038ae63cfe841354c8aba363632344"
+  integrity sha512-0ikrnug3/IyneSHqCBeslAhlK2aBfYek1fGo4bP4QnZPmiqSGRK+Oy7ZMisLWkesffJvQ1cqAcBnJC+8+nxIAg==
+
 "@types/node-fetch@^2.5.0", "@types/node-fetch@^2.6.4":
   version "2.6.11"
   resolved "https://registry.yarnpkg.com/@types/node-fetch/-/node-fetch-2.6.11.tgz#9b39b78665dae0e82a08f02f4967d62c66f95d24"