With the increasing importance of policy issues for science and technology and the growing role of scientific knowledge in policy making, the executive branch has steadily expanded its research and analytical capabilities. On the other hand, the legislative branch has lagged behind in such empowerment, in spite of the current expectation for a stronger legislative initiative and an increasing number of legislative bills about science and technology. In this paper, we compare the capability in Japan with that in the United States and find that the National Diet of Japan is characterized by a fewer institutions, smaller budgets, and a smaller number of expert staffers. It is desirable to enlarge the institutions, financial resources, and staff size of scientific advice to the Diet in order to effectively utilize the outcomes of science of science, technology, and innovation policy. Possible channels through which scientific advice flows to the legislative branch are numerous, ranging from supporting bodies within the legislature, a national academy, and interns at the parliament. They should cover (1) promotion of research and development and evaluation of its benefits and consequences; (2) exploration of scientific evidence and knowledge for policy making and analysis; and (3) assessment of potential impact of science and technology (e.g., technology assessment in a narrow definition).