Masao Saneyoshi graduated from Political Science Department of Tokyo University (1917).
Masao Saneyoshi entered Shokin Ginko (Yokohama Specie Bank). Entered Shima Boeki Kaisha (Shima Foreign Trade Company) (1921) and became its director and president (since 1928) of Nihon Benzine Manufacturing Company. Appointed chief director of Dojima Rice Exchange in Osaka (1932), director of Osaka Stock Exchange, Japan Rice Exchange and Shokuryo Eidan (Food Corporation) (1936), director of Teikoku Sangyo Kaisha (Teikoku Industrial Company) (1943) and a few other industrial and commercial companies. Became director (1947), auditor (1949) and then chairman (since 1952) of Okanishi Trading Company.