It has a general tendency that the political process of Japan，judging from the management cycle，has made more light of Evaluation process than Planning and Practice process. However，the policy evaluation will be strengthened in all governmental organizations setting the period for the reorganization of the Ministries and the Agencies on January 2001. On the other hand，the social policy experiments are grown from the natural science field，but there are less examples in Japan than in U.S.A. and European countries，because of this experiments have the ethical problems. In this paper，I will discuss about the concept and some techniques of the social policy experiments with a few examples，and the relation between the policy evaluation and the policy experiments.