diff --git a/CHANGELOG.md b/CHANGELOG.md
index 54fbb0412..f4fe8de75 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -19,6 +19,9 @@
 - Fix: v2023.12.0で追加された「モデレーターがユーザーのアイコンもしくはバナー画像を未設定状態にできる機能」が管理画面上で正しく表示されていない問題を修正
 - Enhance: チャンネルノートのピン留めをノートのメニューからできるよ
 
+### Server
+- Enhance: ActivityPub Deliver queueでBodyを事前処理するように (#12916)
+
 ## 2023.12.2
 
 ### General
diff --git a/packages/backend/src/core/QueueService.ts b/packages/backend/src/core/QueueService.ts
index be378a899..4f99dee64 100644
--- a/packages/backend/src/core/QueueService.ts
+++ b/packages/backend/src/core/QueueService.ts
@@ -16,6 +16,7 @@ import type { DbQueue, DeliverQueue, EndedPollNotificationQueue, InboxQueue, Obj
 import type { DbJobData, DeliverJobData, RelationshipJobData, ThinUser } from '../queue/types.js';
 import type httpSignature from '@peertube/http-signature';
 import type * as Bull from 'bullmq';
+import { ApRequestCreator } from '@/core/activitypub/ApRequestService.js';
 
 @Injectable()
 export class QueueService {
@@ -74,11 +75,15 @@ export class QueueService {
 		if (content == null) return null;
 		if (to == null) return null;
 
+		const contentBody = JSON.stringify(content);
+		const digest = ApRequestCreator.createDigest(contentBody);
+
 		const data: DeliverJobData = {
 			user: {
 				id: user.id,
 			},
-			content,
+			content: contentBody,
+			digest,
 			to,
 			isSharedInbox,
 		};
@@ -103,6 +108,8 @@ export class QueueService {
 	@bindThis
 	public async deliverMany(user: ThinUser, content: IActivity | null, inboxes: Map<string, boolean>) {
 		if (content == null) return null;
+		const contentBody = JSON.stringify(content);
+		const digest = ApRequestCreator.createDigest(contentBody);
 
 		const opts = {
 			attempts: this.config.deliverJobMaxAttempts ?? 12,
@@ -117,7 +124,8 @@ export class QueueService {
 			name: d[0],
 			data: {
 				user,
-				content,
+				content: contentBody,
+				digest,
 				to: d[0],
 				isSharedInbox: d[1],
 			} as DeliverJobData,
diff --git a/packages/backend/src/core/activitypub/ApRequestService.ts b/packages/backend/src/core/activitypub/ApRequestService.ts
index b59ce5241..e165c5e96 100644
--- a/packages/backend/src/core/activitypub/ApRequestService.ts
+++ b/packages/backend/src/core/activitypub/ApRequestService.ts
@@ -34,9 +34,9 @@ type PrivateKey = {
 };
 
 export class ApRequestCreator {
-	static createSignedPost(args: { key: PrivateKey, url: string, body: string, additionalHeaders: Record<string, string> }): Signed {
+	static createSignedPost(args: { key: PrivateKey, url: string, body: string, digest?: string, additionalHeaders: Record<string, string> }): Signed {
 		const u = new URL(args.url);
-		const digestHeader = `SHA-256=${crypto.createHash('sha256').update(args.body).digest('base64')}`;
+		const digestHeader = args.digest ?? this.createDigest(args.body);
 
 		const request: Request = {
 			url: u.href,
@@ -59,6 +59,10 @@ export class ApRequestCreator {
 		};
 	}
 
+	static createDigest(body: string) {
+		return `SHA-256=${crypto.createHash('sha256').update(body).digest('base64')}`;
+	}
+
 	static createSignedGet(args: { key: PrivateKey, url: string, additionalHeaders: Record<string, string> }): Signed {
 		const u = new URL(args.url);
 
@@ -145,8 +149,8 @@ export class ApRequestService {
 	}
 
 	@bindThis
-	public async signedPost(user: { id: MiUser['id'] }, url: string, object: unknown): Promise<void> {
-		const body = JSON.stringify(object);
+	public async signedPost(user: { id: MiUser['id'] }, url: string, object: unknown, digest?: string): Promise<void> {
+		const body = typeof object === 'string' ? object : JSON.stringify(object);
 
 		const keypair = await this.userKeypairService.getUserKeypair(user.id);
 
@@ -157,6 +161,7 @@ export class ApRequestService {
 			},
 			url,
 			body,
+			digest,
 			additionalHeaders: {
 			},
 		});
diff --git a/packages/backend/src/queue/processors/DeliverProcessorService.ts b/packages/backend/src/queue/processors/DeliverProcessorService.ts
index 4a1d9f28b..675eccbe3 100644
--- a/packages/backend/src/queue/processors/DeliverProcessorService.ts
+++ b/packages/backend/src/queue/processors/DeliverProcessorService.ts
@@ -72,7 +72,7 @@ export class DeliverProcessorService {
 		}
 
 		try {
-			await this.apRequestService.signedPost(job.data.user, job.data.to, job.data.content);
+			await this.apRequestService.signedPost(job.data.user, job.data.to, job.data.content, job.data.digest);
 
 			// Update stats
 			this.federatedInstanceService.fetch(host).then(i => {
diff --git a/packages/backend/src/queue/types.ts b/packages/backend/src/queue/types.ts
index 9330c0152..5a9952e80 100644
--- a/packages/backend/src/queue/types.ts
+++ b/packages/backend/src/queue/types.ts
@@ -15,7 +15,9 @@ export type DeliverJobData = {
 	/** Actor */
 	user: ThinUser;
 	/** Activity */
-	content: unknown;
+	content: string;
+	/** Digest header */
+	digest: string;
 	/** inbox URL to deliver */
 	to: string;
 	/** whether it is sharedInbox */