Masataro Sawayanagi graduated from Tokyo University (1888). Received Doctor of Letters.
Masataro Sawayanagi became an Education Ministry official and elected a member of the Imperial Academy and appointed president of the Imperial Education Association and Textbooks Investigation Council.
After 1914, he endeavored to popularize liberal education as director of the Seijo Primary and Middle schools, which are private institutions.
He was selected as a member of the House of Peers in 1909.