This article analyzes the social changes and civilian massacres occurred in Seongju, Gyeongsangbuk-do from the beginning of the Korean War to the North Korean People’s army’s retreat under the UN troops. The Korean War occurred in the process of establishing of two disparate divided nations after liberation. Therefore, the nature of civil war was intrinsic to the Korean War. In this reason, a conflict between the left and right wing in this war was sharp and, as a result, a large-scale civilian casualties occurred. In the case of Seongju, there were the representative examples: Bodo League members genocide by the police in the opening of the war, rightists massacre by security units for the North Korean People’s army Occupation period, war forced labour’s genocide by police after UN forces’ restoration and so on. In addition, North Korea invasion of South Korea across the Korean peninsula was aimed at establishing DPRK(Democratic People’s Republic of Korea) in the country. Accordingly, People’s Committee and the Labor Party were organized and the land reform and war mobilization in Seongju were carried out. This article explains the social changes in the early days of Korean War and the reality repeated by the left and right wing, and illuminates the impacts of changes in the community. (Keymyung University / ykl311@kmu.ac.kr)