To further improve productivity of a cam and to reduce cost by eliminating finishing work at the time of manufacturing the cam and decreasing the number of working mandays of a cam surface forming member in a previous process of cam formation.

In this manufacturing method of a cam, at least an overall surface of a cam surface of a lobe part of a cam main body is formed out of a thin metal plate 7. Cam surface molding surfaces 10a 11a, 12a, 13a of molds 10, 11, 12, 13 are formed so as to have a shape, roughness and dimensional precision of the cam surface in a cam completed state, and the thin metal plate 7 is set on the cam surface molding surfaces 10a, 11a, 12a, 13a. Thereafter, a cam surface is formed by deforming the thin metal plate 7 so as to copy the cam surface molding surfaces 10a, 11a, 12a, 13a by pressure of resin which is a material to form the cam main body to be injected in the molds 10, 11, 12, 13 in a melting state.