The Administrative Court Organization Act Article 3

Trials in the High Administrative Court are conducted by a collegial panel of three judges. However, the review of summary proceedings, traffic adjudication proceedings and detention sanction proceedings at a District Administrative Litigation Division are conducted by a single judge. Trials in the Supreme Administrative Court, unless otherwise prescribed by law, are conducted by a collegial panel of five judges.
中文原文 行政法院組織法第3條
高等行政法院之審判,以法官三人合議行之。
但地方行政訴訟庭審理簡易訴訟程序、交通裁決事件程序及收容聲請事件程序,以法官一人獨任行之。
最高行政法院之審判,除法律另有規定外,以法官五人合議行之。

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