Honorable Hamada graduated in 1960 from the Law Faculty of the University of Tokyo and after finishing the stint at the Legal Training and Research Institute, the Supreme Court of Japan, was registered in 1962 as attorney-at-law in Tokyo. He studied at Harvard Law School and received LL.M. degree in 1966. During 1966 and 1967, Justice Hamada clerked at a small firm in New York City specialized in U. S.-Japan trade. Back in Japan, his fields of practice were mainly international business transactions, with particular emphasis on international securities and finance markets. He was instrumental in opening up the Japanese capital markets to foreign issuers. Hamada & Matsumoto, before its merger with Mori Sogo in 2002 to form Mori Hamada & Matsumoto, was well-known for its activities in the European Capital Markets.

For a few years before his appointment as an Associate Justice of the Supreme Court in May, 2001, Justice Hamada was involved with large-scale insolvency cases such as Bearing Securities, Nippon Credit Bank and Yamaichi Securities. Since his retirement from the bench in May 2006 at the compulsory retirement age of 70, he has been back in private practice. His recent activities are related mostly to public interest issues such as promotion of Lay-Judge Criminal Trial System, Sun-based Economy for stepped-up use of renewable energy sources and the World Justice Project. Justice Hamada is a Financial Expert appointed by P.R.I.M.E. Finance, an international arbitration/mediation organization for international financial disputes created in the Hague, January 2012.