diff --git a/packages/misskey-bubble-game/build.js b/packages/misskey-bubble-game/build.js
index baf8f7d4a5d0..0b79f4b9159b 100644
--- a/packages/misskey-bubble-game/build.js
+++ b/packages/misskey-bubble-game/build.js
@@ -23,6 +23,9 @@ const options = {
 	sourcemap: 'linked',
 };
 
+// built配下をすべて削除する
+fs.rmSync('./built', { recursive: true, force: true });
+
 if (process.argv.map(arg => arg.toLowerCase()).includes("--watch")) {
 	await watchSrc();
 } else {
diff --git a/packages/misskey-js/build.js b/packages/misskey-js/build.js
index baf8f7d4a5d0..0b79f4b9159b 100644
--- a/packages/misskey-js/build.js
+++ b/packages/misskey-js/build.js
@@ -23,6 +23,9 @@ const options = {
 	sourcemap: 'linked',
 };
 
+// built配下をすべて削除する
+fs.rmSync('./built', { recursive: true, force: true });
+
 if (process.argv.map(arg => arg.toLowerCase()).includes("--watch")) {
 	await watchSrc();
 } else {
diff --git a/packages/misskey-reversi/build.js b/packages/misskey-reversi/build.js
index baf8f7d4a5d0..0b79f4b9159b 100644
--- a/packages/misskey-reversi/build.js
+++ b/packages/misskey-reversi/build.js
@@ -23,6 +23,9 @@ const options = {
 	sourcemap: 'linked',
 };
 
+// built配下をすべて削除する
+fs.rmSync('./built', { recursive: true, force: true });
+
 if (process.argv.map(arg => arg.toLowerCase()).includes("--watch")) {
 	await watchSrc();
 } else {