A product of a modern policy-making system, a think tank represents the trend of making policies in a scientific way. It also constitutes an important component of national soft power. As think tanks become increasingly involved in the process of public policy-making, their influence receives more and more attention. They are even referred to as the “fifth power” after legislation, administration, judiciary and news media. The science of science, technology and innovation policy renders crucial knowledge support to the development of a think tank. Japan is the second country, after the United States, to promote the development of the science of science, technology and innovation policy as an academic discipline at the national level. To facilitate the development of the science of science, technology and innovation policy, the Japanese government has launched special programs and gained valuable experience in its implementation.