In this research project, I will investigate how both countries, Japan and U.S., will deal with the issue of increasing international capital mobility under the globalization from comparative perspectives, by reforming corporate taxes, which is one of the most responsive taxes to globalization. In response to globalization, the governments in OECD countries have reduced drastically their corporate tax rates by average 20% points since 1980's and simultaneously widened their tax bases so that they can strengthen their competitiveness and secure tax revenues. This trend is called "tax competition". The directions both countries will take regarding their corporate tax reforms could have huge impacts on the developed as well as developing countries' future tax reforms, since they have still the highest corporate tax rates among the OECD countries; hence they are facing common tasks. The objective of this research is to clarify future visions of corporate taxes through comparative study of corporate tax reforms in Japan and U.S. For this purpose this project will be divided into three subtopics: (1) Japanese and U.S. corporate tax reforms at federal/national level, (2) Effectiveness of utilizing corporate tax as economic policy instrument, and (3) Japanese and U.S. corporate tax at state/prefecture level. Methodology of this research is based on (1) literature survey, (2) interviews to key persons, and (3) collection and analysis of tax data. For Japan, "Report about the Investigation Results on the Tax Preferences Applied" issued yearly by the Ministry of Finance offers individual as well as aggregated data for all the Japanese corporate tax preferences. For U.S., Treasury Department Office of Tax Committee (OTA) and Joint Committee on Taxation (JCT) make all the data and their outcome of analysis open to the public. This rich information makes me possible to analyze the revenue loss, policy effectiveness, different influences to various industrial sectors, etc. This is the first research trial to make a comprehensive comparative analysis of Japan-U.S. corporate tax reforms both at federal/national and state/prefecture level under the globalization, as far as I know. Especially, the research on tax preferences could make an important contribution to fill a blank in the Japanese corporate tax researches to date. While many theoretical as well as empirical research results relating to tax preferences can be found in U.S., those are rare in Japan due to the lack of tax data. Research period of this project is just parallel to the duration of the scheduled Japanese corporate tax reform. In this point I would like to stress that this research has not only academic significance, but also rich policy relevance, since this project will proceed in the interaction with the policy debate about the Japanese corporate tax reform. The knowledge acquired from the project can thus contribute to keep the right way for the appropriate tax reform. The applicant has joined the governmental tax committee under Abe administration since May 2013. After my returning to Japan I will further contribute to the policy debate around corporate tax reform based on this research project.