Purpose: This study introduces the idea of "Kyouzai Kenkyuu" and examines its potentiality as a conceptual tool to point to the curriculum design process with a case of social science education. By doing so, this study can contribute to expanding the target of reflection from the practices "inside" classrooms toward the curriculum design "outside" classrooms and the strengthening of teacher professionalism by understanding teachers as curriculum designers. Approach: The authors utilised literature review to illustrate how "Kyouzai Kenkyuu" can be a conceptual tool to point to the curriculum design process. Subsequently, the authors conducted interpretative practitioner research to showcase how "Kyouzai Kenkyuu" can be taught in pre-service teacher education and how teacher educators can educate pre-service teachers as curriculum designers utilising insider's perspectives. Finally, the authors discussed the potential of "Kyouzai Kenkyu" as a conceptual tool to indicate the content and method of designing the curriculum and as an approach to enhance teachers' development as curriculum designers. Findings: "Kyouzai Kenkyuu"--"Kyouzai" meaning learning material(s) and "Kenkyuu" meaning study or research in the Japanese language--is a practice for curriculum design and one of the dispositions to define teachers as professionals. In Japan, teachers are expected to be practitioners who conduct "Kenkyuu" (research) about discipline, students, and the context surrounding students to design suitable "Kyouzai" (learning material[s]) and a curriculum for individual classrooms. In method courses, pre-service teachers verbalize and reflect on their "Kyouzai Kenkyuu" and how it impacts curriculum design. Through these experiences, social science teachers in Japan can enjoy the opportunities to develop their design and teaching rationales. Research limitations: This study is limited to three method courses that the authors have taught; thus, the findings on how to teach "Kyouzai Kenkyuu" may not be generalizable.