In this research, we analyzed the activities of Japanese architectural offices in Korea during the Japanese occupation era, classifying them into two groups: first, Japanese architectural offices that had their bases in Korea, and second, Japanese architectural offices that had their bases in Japan. There were totally 98 Japanese architectural offices that had their bases in Korea during the Japanese occupation period. The number of those offices had increased rapidly since 1920s. Nakamura(the design of bank buildings), Tamada(the design of theaters), Otsumi(the design of Japanese style residential houses) can be regarded as the most remarkable Japanese architectural offices among them. We found that these offices already specialized in certain architectural planning fields, such as bank buildings, theaters and residential houses. It was also found that, during the Pacific War period, even privately-managed architectural offices were mobilized for the war by Japanese government, through designing munitions factories, etc. On the one hand, since some large Japanese corporations entered into Korea, many Japanese architectural offices, that had their bases in Japan, got into working in Korea and designed a number of buildings, with the exception of the architectural office of Vories, who was a Christian architect. Even though the place that the activities of these Japanese architectural offices were carried out was Korea, any factors of Korean architectural style couldn't be found In their works. This means that they just transplanted the Japanese modern architectural style in Korea.