To increase the life-span of a piston by forming a reinforcing ring with a sintering material which includes a copper alloy phase, an iron alloy phase, and carbide, and has a hardness higher than a piston body, and fixing the reinforcing ring to at least one surface of a ring-shaped groove of the piston body by means of casting-in.

In a piston body 1 provided with three ring-shaped grooves 2 to 4 on an outer peripheral surface 1a of an aluminum alloy piston, a reinforcing ring 11 formed with a ring-shaped recess part 14 is fixed on the top ring- shaped groove 2, and piston ring is equipped to each of the ring-shaped recess part 14, and the ring-shaped groove 3, 4. Such a reinforcing ring 11 is formed from a composition made of 10 to 40% copper, 4 to 20% nickel, 2 to 15% chromium, 0.05 to 2.0% carbon, and the remainder of iron, as weight criterion, and is fixed to the ring-shaped groove 2 by casting-in with an aluminum alloy molten metal, thereby improving integration by casting-in and mold strength of a cast-in interface.