A theoretical composition is drawn for the professional development of teacher educators. In this study, we focused on Dr. Anja Swennen and Dr. Kari Smith, who are actively engaged in teacher education research. Dr. Swennen focused on the theory of professional development in internal disciplines and expects teacher educators to work on their own professional development. On the other hand, Dr. Smith explored the ability to prove theories based on external criteria and advocates the importance of systematic professional development. By absorbing their theories, we obtained the two suggestions for Japanese teacher education reform. First, it is necessary to nurture the expertise of teacher educators responsible for student teaching and beginning teachers’ training intentionally and systematically. Second, it is also necessary to position this expertise to nurture teachers in the qualities and abilities that should be cultivated in professional school for teacher education. From this perspective, we obtained a design for the professional development of teacher educators.