A motorcycle frame is provided such that the spacing between a main frame and a side plate can be easily adjusted, and joint surfaces, at which the side plates and engine hangers abut the main frame, can be easily formed. Each side plate is provided with upper and lower plate-side bosses used for adjusting the spacing between itself and a main frame. A surface of an upper first boss of the main frame, which abuts on the upper plate-side boss, and surfaces of upper second bosses of the main frame, which abut on an upper engine hanger, are provided on the same plane. In addition, a surface of a lower first boss of the main frame, which abuts on the lower plate-side boss, and surfaces of lower second bosses of the main frame, which abut on a lower engine hanger, are provided on the same plane.