To cast a reinforcing member in a pin boss part, so as to prevent lightening of weight from being obstructed in a piston main body, improve strength and wear resistance of a pin hole part serving as a slide contact surface of a piston pin, in a piston for an internal combustion engine.

In a piston for an internal combustion engine with a piston main body 1 constituted by materials 1A, 1B of different strength, the piston main body 1 is primarily molded by forging a compound material consisting of the piston base material 1B and the material 1A of strength higher than that, so as to constitute at least partly a pin hole part 6 of the piston main unit 1, serving as a slide contact part of a piston pin, by the material 1A of high strength.