Industrial Group Act Article 13

All licensed publicly-operated and nongovernmental-run factories must join in the relevant industrial trade associations within one month after establishment except for ordnance factories of national defense; multi-occupation enterprises should join all the relevant industrial trade associations respectively.All member enterprises or factories of industrial trade associations have to send their member representatives to attend meetings convened by industrial trade associations.
中文原文 工業團體法第13條
同一區域內,經依法取得工廠登記證照之公營或民營工廠,除國防軍事工廠外,均應於開業後一個月內,加入工業同業公會為會員;其兼營兩種以上工業者,應分別加入各該業工業同業公會為會員。
前項會員應派代表出席工業同業公會,稱為會員代表。

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