This paper aims to clarify the background of the modernization of theater architecture in Japan during the 1920-30s. After the Meiji era, Western-style theaters were gradually constructed in Japan. In particular, starting in the mid-1920s, after the Great Kanto Earthquake, the modernization of theaters progressed rapidly. This paper identifies two characteristic movements in Japan’s theaters modernization by analyzing journal articles and academic books of the time: the Society for the Study of Theater Architecture and Renshichiro Kawakita.