This study focused on epistemological beliefs, which is a system of beliefs about the nature of knowledge and process of knowing that learners participating in classroom communication have. The purpose of this study is to prove the hypothesis that learners' epistemic beliefs influence classroom communication participation and that their experience of classroom communication, in turn, affects their reformation of epistemological beliefs. This study quantitatively analyzed the relationship between epistemological beliefs, participation in classroom communication, and experience of 287 middle and high school students using survey research methods. The results of the research can be presented in three points. First, the belief that experts are the sources of knowledge negatively affects students' participation in small group dialogues. Second, students with more experience in group activities have more sophisticated beliefs in knowledge source than students without experience. Third, epistemological beliefs of high school students are simpler than those of middle school ones in terms of knowledge source and learning ability. Therefore, it will be important to provide a rich experience of meaningful small group conversations for high school students, as well as broaden their perspectives and expand their thinking about a specific knowledge by asking open questions in class. This study is meaningful in that it expands current knowledge on speech communication education by showing the importance of learner's belief in the process of acquiring knowledge in classroom communication.