The Constitution of Japan, enacted on November 3, 1946, and effective as of May 3, 1947, gave the judicial power to the Supreme Court and the inferior courts established by the Diet, the national legislature, and gave the power of judicial review to the judiciary. Equipped with the power of judicial review, the Japanese Supreme Court was expected to perform a very significant political role in safeguarding the Constitution, especially its Bill of Rights, against infringement by the government. Yet, it has developed a very conservative constitutional jurisprudence ever since its establishment. This article examines why the Japanese Supreme Court has developed such a conservative constitutional jurisprudence. First, the power of judicial review and the system of judicial review in Japan in examined. Second, it points out how the Japanese Supreme Court is reluctant to entertain constitutional litigation and how the Japanese Supreme Court is unwilling to apply close scrutiny or strike-down statutes. Finally, the historical, organizational, institutional, and strategic reasons for the conservative constitutional jurisprudence is explored. In conclusion, the author argues that the most fundamental reason lies in the reluctance of Japanese judges to view the Constitution as a source of positive law to be enforced by the judiciary.