diff --git a/CHANGELOG.md b/CHANGELOG.md
index 406f5ba606..e7cfa6dc7d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@
 ### Server
 - Fix: `/api-doc` にアクセスできない問題を修正
 - Fix: support `alsoKnownAs` from remote actors as either array or unwrapped singleton
+- Fix: ローカルに存在しないリモートアカウントに対するアカウント削除リクエストを受信した際に、そのユーザーを新規作成して削除する挙動を修正
 
 ## 2026.3.2
 
diff --git a/packages/backend/src/queue/processors/InboxProcessorService.ts b/packages/backend/src/queue/processors/InboxProcessorService.ts
index 079e014da8..75e2d0753e 100644
--- a/packages/backend/src/queue/processors/InboxProcessorService.ts
+++ b/packages/backend/src/queue/processors/InboxProcessorService.ts
@@ -13,7 +13,7 @@ import { FetchInstanceMetadataService } from '@/core/FetchInstanceMetadataServic
 import InstanceChart from '@/core/chart/charts/instance.js';
 import ApRequestChart from '@/core/chart/charts/ap-request.js';
 import FederationChart from '@/core/chart/charts/federation.js';
-import { getApId } from '@/core/activitypub/type.js';
+import { getApId, isActor, isDelete } from '@/core/activitypub/type.js';
 import type { IActivity } from '@/core/activitypub/type.js';
 import type { MiRemoteUser } from '@/models/User.js';
 import type { MiUserPublickey } from '@/models/UserPublickey.js';
@@ -84,6 +84,23 @@ export class InboxProcessorService implements OnApplicationShutdown {
 			return `Old keyId is no longer supported. ${keyIdLower}`;
 		}
 
+		{
+			let userExistenceCheckApId: string | null = null;
+
+			// 存在しないActorに対するActorのDeleteアクティビティは無視する。
+			// actorとobjectが同じならばそれはActorに違いない
+			if (isDelete(activity) && typeof activity.object === 'object' && (isActor(activity.object) || getApId(activity.actor) === getApId(activity.object))) {
+				userExistenceCheckApId = getApId(activity.object);
+			}
+
+			if (userExistenceCheckApId != null) {
+				const user = await this.apDbResolverService.getUserFromApId(userExistenceCheckApId);
+				if (user == null) {
+					throw new Bull.UnrecoverableError(`skip: user not found for delete activity. ${getApId(userExistenceCheckApId)}`);
+				}
+			}
+		}
+
 		// HTTP-Signature keyIdを元にDBから取得
 		let authUser: {
 			user: MiRemoteUser;