Graduated from Ship Engine Department of Osaka Higher Engineering School.
Nobuharu Oki entered Engineering Department of Kure Naval Arsenal (1911). Made an official tour of England for one year (1921-1922). Appointed naval engineer (1923). Retired from government service (1940). He became chief engineer, director and then managing director of Tokyo Tankosho and became director of Ishikawajima Zosenjo (Shipyard) Company (1944). Resigned same company and reinstated as managing director of Tokyo Tankosho (1945). Served as superintendent of Osaki Plant of Tokyo Tankosho (1945-1946). Later appointed its senior managing director (1950) and then president.