The purpose of this research is to reveal constitution of beliefs of lesson of an elementary school teacher who practices “Manabiai”. Though many previous study has researched the excellent teachers’ beliefs, we research beliefs of a young teacher who said to be a “eager but ordinary” by the former school superintendent who knows teachers in a city well. The life history the teacher wrote, supplemental interview data, and the record of post-lesson conference of his research lesson are qualitatively analyzed, then the constitution of his beliefs of lesson is represented graphically. The result of this study has three points. First, the teacher puts emphasis on not students talking but listening. Second, the teacher emphasizes that all student are able to learn by listening to others’ utterances. Third, the teacher has a vision that students’ inner logics and feelings emerge through studying by a learning material. We consider that collaborative reflection with colleagues in in-school lesson study has influence the teacher to form the beliefs, and whole city educational policy support the lesson study as a background.