The purpose of this study is to clarify the process of labor negotiation by Japan Professional Baseball Players Association （JPBPA） in order to capture the change of the status of the players, who are the important persons concerned in the professional baseball world. This article focuses the period from 1993, when a free agent （FA） system was introduced to 2004, when the JPBPA went on strike for the first time in baseball history in Japan.
After introduction of a FA system, the JPBPA continued to succeed in a certain level of improvement of the working conditions.
And, since 1999, the JPBPA addressed the structural improvement of the baseball world as new movements.
However, the Nippon Professional Baseball Organization （NPB） often made the player’s working conditions worse without the JPBPA’s recognitions. The worst of them was the baseball alignment in 2004. The JPBPA engaged in collective bargaining and strike with their legal rights as a labor union. As a result, they stopped reduction of the number of the clubs, stopped making their working conditions worse, and obtained the chances of discuss about structural improvements of Japanese professional baseball with the NPB.
We should pay attention to having gained such achievements by the JPBPA under the condition which the NPB seems to lead the process of the negotiation.

抄録全体を表示