Basic Code Governing Central Administrative Agencies Organizations Article 18

The head of single-head agencies shall be called a “Minister”. The head of council/commission-type agencies shall be called a “Minister”. However, titles for heads of agencies with special functions shall bestipulated separately.The heads of first-level and second-level agencies shall be political posts.The heads of third-level agencies shall be ex-officio posts, unless otherwise specified because of special functions or by law. The heads of fourth-level agencies shall be ex-officio posts.Unless otherwise stipulated by laws due to special functions, agency heads shall be full-time posts.
中文原文 中央行政機關組織基準法第18條
首長制機關之首長稱長或主任委員,合議制機關之首長稱主任委員。
但機關性質特殊者,其首長職稱得另定之。
一級、二級機關首長列政務職務;三級機關首長除性質特殊且法律有規定得列政務職務外,其餘應為常務職務;四級機關首長列常務職務。
機關首長除因性質特殊法規另有規定者外,應為專任。

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