The purpose of this paper is to examine the trends in social mobility in postwar Japan. We obtained the following results based on the SSM survey data. First, the importance of education in status attainment has increased. It can be explained naturally by the decline of self-employed sectors. Secondly, while this trend increased society's openness to some extent, a class difference in educational opportunity remains the same as it was in the past. Thirdly, the linkage between education and occupational status hasn't changed in spite of upgrading in the level of education of workers. The same observation applies to the middle stage of careers beyond the entrance stage. Furthermore, the difference in attainment made by university's academic prestige is stable. It seems reasonable to conclude that our society has maintained the same mobility structure for these decades.