‘The Act on the prevention of and countermeasures against violence in schools’was enacted in 2004. Since then, the law has been revised 19 times partially or wholly. This study aimed to investigate what has been changed and what factors would affect such changes since its establishment from the perspective of historical new institutionalism, particularly three aspects of structure, institution, and actors. The findings of the study were as follows; first, looking at the structural aspect, critical junctures in revisions of the school violence law were more related to school violent incidents that were socially shocked and resulted in breaking path dependency; second, as from the institutional aspect, the concept of school violence and its range were expanded in the revisions and governmental policies have focused on creating relevant school environment and building social infra system for safer school life; third, actors involved officially or unofficially in revising the school violence law utilized moderate ways such as media interviews to revise the law rather than radical demonstrations. From these findings, the study suggest that for better prevention of school violence law revisions and policy reforms of school violence should be made based on reliable predictions of school violence and much understanding of students in adolescence. In addition, social empathy and solidarity should be built and strengthened to prevent and root out violence in schools.