This study examines the Korean minorities unification movement of Japan since the postwar era. When Japan defeated the Pacific war, about 2.3 million Korean minorities existed in Japan. During the war the Japanese government treated Korean minorities as Japanese, but after the war Korean minorities realized they were no longer Japanese because the Korean peninsula became an independent country. Therefore, the Korean minorities in Japan started to organize Korean societies to protect their rights and interests. The early post-war Korean societies in Japan were consisted of from left and right, but on May 1946, the various phases of the purge aimed at the right wing, eventually lead to the advent of the leftist and other radicals. During 1946, the purge might have had it greatest influence on every important category of Korean societies in Japan. Subsequent to the summer of 1948, the purge became a holding operation. The “reverse course” which dominated the formulation of policy during the occupation`s later years(1948-1952) also influenced the implementation of the purge. By contrast, in 1950 SCAP utilized the purge to remove the leadership of the Korean societies in Japan and the Japan Communist party. The occupation objective that emerged in Japan from the period of tutelage with a leadership of moderates was compromised by the timing of the so called red purge, for the latter coincided with the release from designation of the extreme right Korean societies in Japan. Finally, the Korean societies in Japan separated into left and tight, which supports to North(DPRK) and South(ROK) regime. In addition, this paper describes how Korean societies in Japan aimed toward the Korean peninsula unification.