School bullying is one of the most important problem we must solve, but we have never found clues of solution. This study examines a school bullying by MAS (Multi-Agent System) method, based on an assumption that the bullying emerges from perspective of student-student interaction [9]. In the report, we presented two improved models based on the original model [9], "Teacher-agent added model" and "Substituted conformity model". Then, by simulating these models, we proposed to understand group formation dynamics and the bullying structure.