Abstract. In a society, we have many forms of relations with other people from home, work or school. These relationships give rise to a social network. People in a social network receive, provide and pass lots of information. We often observe that there are a group of people who have high influence to other people. We call these high influence people opinion leaders. Thus, it is important and useful to identify opinion leaders in a social network. In Web 2.0, there are many user participations and we can create a social network from the user activities. We propose a simple yet reliable algorithm that finds opinion leaders in a cyber social network. We consider a social network of users who rate musics and identify representative users of the social network. Then, we verify the correctness of the proposed algorithm by the T-test.