PURPOSE: To improve the dimensional precision and the casting surface precision at a casting step and to make the following work unnecessity, related to the shaft part and the shaft hole in a suspension arm as a casting product.

CONSTITUTION: In a mold 1 for casting the suspension arm composed of a sand mold, a hollow cylindrical core 9 or 10 formed with a ceramic is arranged to a part directly used to the formation of the outer peripheral surface 8a of a pin 8 for connecting part with the parts at the other side and to a part directly used to the formation of the inner peripheral surface 7a of the same cylindrical part 7. The inner diameter of each core 9, 10 is matched to the outer diameter of the pin 8 and also, the outer diameter of each core 9, 10 is matched to the cylindrical part 7 and then, both cores 9, 10 are made to be commonly used to the formation of the pin 8 and the formation of the cylindrical part 7.