This study aims to get ideas for improvement of in-service education for physical education through examining factors which promote transformation of beginning teacher X's thinking in physical education lessons during four years after his recruitment. The results are summarized as following points. The ideas which these process of beginning teacher X's development proposed for professional development about physical education were summarized as following 4 points. 1. Beginning teachers need their mentors' assistance according to their needs and daily discussion with their colleagues of their schools about their pupils. 2. School directors have to esteem their staff ideas and play an important role for creating atmosphere of which school teachers can think of their teaching mainly. 3. Beginning teachers need in-service training where they observe and discuss teaching of physical education and learn physical activities' skill in their schools. 4. School directors, their colleagues and local educational authorities have to assist that beginning teachers partake in an in-service training out of school for professional development of physical education.