diff --git a/CHANGELOG.md b/CHANGELOG.md
index 13c2876a82..af3fc75c06 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -50,6 +50,7 @@ You should also include the user name that made the change.
 - Server: Fix peers API returning suspended instances @ineffyble
 - Server: trim long text of note from ap @syuilo
 - Server: Ap inboxの最大ペイロードサイズを64kbに制限 @syuilo
+- Server: アンテナの作成数上限を追加 @syuilo
 - Client: case insensitive emoji search @saschanaz
 - Client: InAppウィンドウが操作できなくなることがあるのを修正 @tamaina
 - Client: use proxied image for instance icon @syuilo
diff --git a/packages/backend/src/server/api/endpoints/antennas/create.ts b/packages/backend/src/server/api/endpoints/antennas/create.ts
index fe24a10300..2378660ec8 100644
--- a/packages/backend/src/server/api/endpoints/antennas/create.ts
+++ b/packages/backend/src/server/api/endpoints/antennas/create.ts
@@ -26,6 +26,12 @@ export const meta = {
 			code: 'NO_SUCH_USER_GROUP',
 			id: 'aa3c0b9a-8cae-47c0-92ac-202ce5906682',
 		},
+
+		tooManyAntennas: {
+			message: 'You cannot create antenna any more.',
+			code: 'TOO_MANY_ANTENNAS',
+			id: 'faf47050-e8b5-438c-913c-db2b1576fde4',
+		},
 	},
 
 	res: {
@@ -81,6 +87,13 @@ export default class extends Endpoint<typeof meta, typeof paramDef> {
 		private globalEventService: GlobalEventService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			const currentAntennasCount = await this.antennasRepository.countBy({
+				userId: me.id,
+			});
+			if (currentAntennasCount > 5) {
+				throw new ApiError(meta.errors.tooManyAntennas);
+			}
+
 			let userList;
 			let userGroupJoining;