Labor Union Act Article 14

Supervisory employees who represent employer in exercising managerial authority may not join the labor union in that business entity, except where the union charter prescribes otherwise.
中文原文 工會法第14條
代表雇主行使管理權之主管人員,不得加入該企業之工會。
但工會章程另有規定者,不在此限。

English translation for reference only; the Chinese text prevails. Not legal advice.