The objective of this research is to carry out a flow analysis in the Japan Sea using the box model method, consisting of three equations of the conservation of mass, salinity and heat, and to study the reproducibility of its result. The input conditions is the water temperature and salinity supplied by JODC, indicate a characteristic distribution in the Japan Sea, including a cold water area, a warm water area and water mass peculiar to the Japan Sea, meteorological data, river flows and flows at straits. The seasonal variation of the nearshore branch of the Tsushima Warm Current along the Japanese coast, the East Korean Warm Current along the Korean Peninsula and the Liman Current along the continent are reproduced in the results of the flow analysis. However, the overshooting of the East Korean Warm Current to the north occur comparing with the analytical result of OGCM/GFDL. The flow in the intermediate layer is anti-clockwise at the west of Yamato Rise and clockwise at the Yamato Basin similar to the analytical result of OGCM/GFDL. The anti-clockwise flow at the Japan Basin and clockwise flow at the Yamato Basin are seen in the deep layer in winter.