The purpose of this study was not only to develop system of CoP(community of practice) for normalizing PE classes, but also to describe how teachers in community improve their professionalism as a PE teacher. In order to do this, CoP for PE classes in S elementary school was operated for 5 months. The data was gathered by in-depth interviews, participative observation and documents. Collected data was analysed via inductive category analysis. The CoP was operated focused on curriculum reconstruction, practicing PE classes and reflection on teaching as a first action research. The result of first action research showed that, teachers became more confident and had professionalism on operating curriculum, but it was necessary that CoP improve ‘joint enterprise' for developing teacher's professionalism on PE classes. In order to improve the first action research`s result, ‘joint enterprise' of CoP included operating curriculum, preparing classes and on-the-job training for professionalism in second action research. The result of second action research showed some changes as follows : 1) Teachers constructed conditional knowledge together. 2) Quality of interaction was increased between teacher and student. 3) Culture of same-grade teachers became more academical. Therefore, operating CoP showed the possibility to be alternative for normalizing PE classes.