The study addressed the effectiveness of bullying by implementing a bullying prevention program for senior elementary school students. 19, fifth grade students of S Elementary School in Seoul were conducted to assess for the study. The bullying prevention program consists of 12 sessions, which class problem recognition, problem resolution preparation, problem resolution, new hope and a fresh start. the program aims at improving the sense of belonging in class. “Understanding class problems” in the first two sessions; “학급문제해결준비로 나와너의수용, the acceptance of the class community” seven sessions in the middle; “the actual change of the class” two sessions and “the new hope and a fresh start” one session in the latter; a total of 12 sessions were examined. The results of this study were as follows: First, the sense of belonging to the class of the target class increased significantly by the bullying prevention program. Second, bullying was significantly decreased. Third, No significant changes were seen in the defensive role shifts; However, there have been not many defensive role shifts on the qualitative research analysis, it can be seen that the bullying within the class is greatly eased even if the minority children show defensive behavior due to the influence of the program. Therefore, the program was found to be effective in promoting the sense of belonging in class and reducing attacking behaviors such as bullying. The implications of the results and implications of this study, limitations, and suggestions for follow-up studies were discussed.