The purpose of this study is to propose self-study as a way to enhance the professionalism of a teacher by releasing the self-study case of a researcher. There have been various attempts to improve the professionalism of teachers. Teachers are trying to improve their individual expertise through self-study, training courses, guidance & consulting, graduate school and participation in learning communities. However, it is difficult for teachers to improve their professionalism due to the fact that they are made out of external force, and that guidance and training are not so effective. Most of all, teachers do not study 'himself/herself as a teacher' and there is no guidance about how to do it. The purpose of this study is to help the teachers who are concerned about the growth of professionalism by showing the cases how a teacher has improved her expertise through self-study. To do this, the research was carried out as follows. First, I presented the significance of self-study, key elements, and major methods. Secondly, I recorded diachronic self-study case and synchronic self-study case. The diachronic self-study was divided into two parts in order to understand how the researcher's identity as a teacher was formed : from the period of elementary school till the period just before being a teacher and the subsequent process of growth in the teacher community. In order to understand how the researcher's beliefs and identity are revealed in the classroom or to the students in the informal self-study, 50 pre-service elementary teachers of C National University of Education helped the synchronic self-study as critical colleagues in art, social practice, technology. The preliminary teachers' criticism of the researcher's class was analyzed based on Johari's Window and the part of the criticism and the thought of the researcher were included with subtitle. The conclusions of the researcher's self-study are as follows. The point of this study, which began as a question of the professionalism of the teacher, was to find my identity as a teacher and the self-study was used as the method. The process of experiencing a self-study can provide an experience of growth that clearly sees the teacher's own identity. In addition, it is not only able to raise the teacher 's own educational sensibility, but also has an expanding character that fosters the educational sensibility of pre-teachers and fellow teachers. Finally, it is possible to propose a different method of professional growth in pre-service teacher education programs and teacher education programs.