To enhance rotation balance accuracy while suppressing an unbalance amount to be corrected to the minimum at an inspection step after machining when a crankshaft, especially a 3-cylinder crankshaft is manufactured.

In the method for manufacturing the crankshaft, positioning of a center hole becoming machining reference when mechanical machining is performed relative to a shaped material of the crankshaft molded by forging is performed. In a centering step of forming the center hole on the shaped material, first clamp arms 11a, 11b for clamping an end shaft part 101 of the shaped material by approaching to each other on the same linear line and second clamp arms 12a, 12b are provided. The end shaft part 101 is clamped such that a clamp center of the pair of first clamp arms 11a, 11b and a clamp center of the pair of second clamp arms 12a, 12b are coincident with a center of gravity OG of an end surface of the end shaft part 101, a center hole is formed at a position corresponding to the clamp center at that time.