政策合法化，也就是一項特定的政策讓政府所採行，在政策過中乃是非常的重要。因為缺乏此一程序，公眾對政策的接受將會容易瓦解。而在日本，政策合法化的最基本方法，則是由國會通過一項法案，不過法院的判決亦會賦與公共政策的合法性。尤其是在行使違害審查權之際，法院可以透過解釋憲法與法律，加以修正或否決公共政策，因此司法機關就成為了一個重要的政策制定機關。本文便是以憲法案例為主，研究日本之公共政策上的司法影響力。

Policy legitimation, a special policy is adopted by the government, is very important in the policy process. Without it, public acceptance of a policy is easily undermined. In Japan, a common method of policy legitimation is passage of a law by the Diet, but courts decisions also give legitimacy to public policy. Particularly in exercising the power of judicial review, courts can correct or void a public policy through interpreting the Constitution or laws. The judiciary, thus, has become an important policy-making forum. This paper focuses on the constitutional cases and studies judicial influence on public policy in Japan.