Japan was very aggressive before its defeat in World War II. Japan declared its surrender in World War II after the bomb attacking on Hiroshima and Nagasaki done by United States. After its defeat, Japan‟s foreign policy became pasifism. Its pasifism is based on Article 9 Japan‟s Constitution. After more than 70 years, Diet passed the security law on September, 19th 2015 and it took effect on March, 2016. The law extends Japan Self Defense Forces‟ role in international security. This research will search the factors behind the forming of Japan Security Law.