After graduating from the Faculty of Law, University of Tokyo, Hiroshi Terashima joined the Japanese Ministry of Transport in 1965. He held positions as the Director-General of the Chubu District Transport Bureau and the Assistant Vice-Minister, Minister's Secretariat, retiring in 1994.

During his service, he was involved in many national and international maritime transportation projects. He served as the Executive Director of the Nippon Foundation from 1994 until 2002. He is engaged in supporting the building of a cooperative structure to ensure safety in the Malacca and Singapore Straits, anti-piracy initiatives, and human resources development for ocean governance. His ocean policy activities include steering board positions on the Global Forum on Oceans, Coasts and Islands and PEMSEA's EAS Partnership Council. He also played a leading role in the research activities leading to passage of Japan's new Basic Ocean Law.