Regulations on the Permission and Administration of the Employment of Foreign Workers Article 54

Work permits issued to type D foreign workers shall be valid for a maximum of one year.Except during summer and winter vacations, a type D foreign worker with the aforementioned permission to work must not work more than 20 hours a week.
中文原文 雇主聘僱外國人許可及管理辦法第54條
第四類外國人之工作許可有效期間,最長為一年。
前項許可工作之外國人,其工作時間除寒暑假外,每星期最長為二十小時。

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