Migration exchange between Korea and Japan in the first half of the XXth century was one of the most significant factors that influenced economic, social and political situation not only in Korea but also in Japan. This article examines the factors that formed migration flows between Korea and Japan in the framework of the colonial empire. Besides it clarifies the migrants’ role (the Japanese and Koreans) played in the receiving society, as well as it reviews a number of problems caused by immigration processes of the XXth century in the modern Japanese and Korean societies.