The main building, designed by Kingo TATSUNO and Yasushi KATAOKA, is a tile-roofing two-storey building made of Japanese cypress in Momoyama style (luxurious, splendid and decorative style created during Momoyama period).
本館の建築は辰野金吾・片岡安による設計で桃山御殿檜造りの木造2階建て瓦葺き。