The purpose of this paper focuses on the forming condition and its effect of collaborative lesson design between a teacher and two researchers, through Self-Study Methodology. As a result, we clarified main two things as following. The first thing is the differences between the roles of each person in collaborative relationship. In case of the teacher, the role was the make a decision based on feasibility of lesson. In case of the researcher A, the role was to guide the teacher to a certain direction. In case of the researcher B, the roles were to suggest more directions to the teacher than the researcher A, and to regulate among the three including oneself. The second thing is the forming condition of collaboration between research and teacher. We had reflected the teacher`s lessons more than five times. By doing that, we could understand each other`s educational view and bridge the gap of their views about lesson design. This implies that keeping reflection is helpful for better collaborative relationship. Each person recognized different effect from the collaboration. The teacher got a new perspective about lesson design. The researcher A reflected about collaboration process with the teacher. Finally, the researcher B renewed the concept about the desirable relationship between researcher and teacher.