In a crankshaft 200, one hole 213L formed in a crankpin 213 has a bottom surface having a larger area and a depth from a surface of the crankpin less than those of another hole 213M. In forming the hole 213L and the hole 213M, a preformed product 200 of the crankshaft having a shape smaller than that of a cavity is disposed in a die set and punches are simultaneously inserted into the crankpin 213. By this operation, the hole 213L and the hole 213M are simultaneously formed in each crankpin 213 of the preformed product 200.