The aim of this paper was to make clear the criteria of social-conventional judgement through the analysis of children's opinions in moral classes. According to E. Turiel, we judged social-conventions by 6 criteria, especially "rule contingency", "rule alterability" and "authority contingency". These criteria were made through the investigations in U.S.A.. Social-conventions were usually influenced by cultural background, so we needed to make clear the criteria which were suitable for Japanese children. We presented the materials which included social-conventional conflicts, and we asked children the way to solve the problem and the reason why they chose the way. We supposed that children's answers showed us the criteria of social-conventional judgement. The results were as follows. 1) When children solved the social-conventional conflicts, they chose the way according to the "contextualism", especially the relation with another people. 2) This result suggestsed that when we planed moral education, it needed to prepare many experiences that gave children the opportunities to learn what is good and what is bad in the relations with another people.