This study examined students’ self-reported active clarification of their own and other members’ position in group discussion in order to shed light on the relation between students’ beliefs about the nature of knowledge-to-use and their way of participation in cooperative learning. According to their epistemic beliefs, 58 (14 male and 44 female) undergraduate students were assigned to 3 type of groups, including sophisticated (i.e., assuming a wide applicable scope of knowledge and considering prior conditions for application), naïve, and mixed. The results demonstrated that students with sophisticated beliefs in mixed-group rated their own clarification higher compared to students with naïve beliefs and to students in sophisticated-group. It is discussed that the gap of beliefs provided different ways of argument among students, leading a demand to clarify their stance each other and offering a comparative advantage for students with sophisticated beliefs.