In this paper, a study on Mr. Kiyoshi Masuda, an architect, who had not ever been noticed, was made within the range of possibility, an investigation on his major architecture activities was done along with getting his career clear. Secondly, the relation of Mr. Kiyoshi Masuda with the design of the government office building of Hiroshima city was made clear, after clarifying his architecture activities in Hiroshima, especially analyzing the design process of the government office building of Hiroshima city. And then, the reason why Mr. Kiyoshi Masuda was specified to design the buildings built in Hiroshima, and those building are respective characteristics and common characteristics were made clear. That is to say, by considering the architecture activities of one architect, some activity in formations of the architects from the late Taisho period to the early Showa period in Japan, especially in Hiroshima, were introduced in this paper.