A crankshaft that can be strengthened in a short time without being subjected to wasteful processing, and that can be strengthened over a wide range. The crankshaft includes a crank pin and a fillet portion of a journal pin. Compressive residual stress is applied to a region on the fillet portion, which extends at almost equal distances to both sides in a circumferential direction from a portion in which the greatest bending load is applied, and a processing depth for applying the compressive residual stress is gradually decreased in a circumferential direction from the center position in which the compressive residual stress is greatest.