To prevent the occurrence of a shrinkage cavity caused by oriented solidification due to rapid cooling effect of a cooling metallic mold.

The whole surface of inner side from the ridge line of outer peripheral surface at the top part of combustion surface of a piston is formed by a top part cooling metallic mold 3, the whole surface of side surface at the lower side from the ridge line at the top part of the piston is formed by a side surface cooling metallic mold 4 and the inner surface of a piston pin hole or the side end surface of a skirt part is formed by a piston pin cooling metallic mold 5 respectively. Each thickness of the cooling metallic molds 3, 4, 5, is regulated to 1/2-2 times of that of each thick part of a cylinder piston to be cast to unnecessitate feeder.