On the study of internal migration in postwar Japan, migration between rural and urban areas has been studied rigorously. But there are quite few studies about the migration between major metropolitan areas in spite of its importance. Based on the Japanese prefectural data for 1955-90, this paper treats two major subjects. The first is to deduce the properties of migration from the actual movement between any two of three major metropolitan areas, (Tokyo, Oosaka and Nagoya major metropolitan areas). The second is to analyse the relationship between net migration of inter major metropolitan areas and regional economic differentials. The results of our analysis is summarized as follows. Firstly the proportion of inter major metropolitan migrants to all inter prefectural migrants has been increasing steadily. Secondly all net migration of each metropolitan areas has been strongly influenced by the excess of inflow to outflow of other major metropolitan areas, especialy after the first oil crisis than before. Thirdly both metropolitan/non-metropolitan per capita disposal income differentials and employee growth rate differentials have a strong positive correlation to the rate of net migration. But those differentials between Tokyo and other metropolitan areas have a weak positive correlation to the rate of net migration. On the case of the migration between metropolitan areas, it seems that employee growth rate differentials have a stronger effect to net migration rate than per capita disposal income differentials.