To straighten the bend of a crankshaft without lowering the fatigue strength in fillet parts by cold roll-working, with high dimensional accuracy, moreover, at high efficiency.

The expansion and contraction amount of arms is measured after cold roll-working of the fillet parts and, with the same cold working roll 5 used for cold roll-working in the case the expansion or contraction amount of the arms is larger than a prescribed amount of expansion or contraction and with the same cold working roll 5 used for cold roll-working in the case the expansion or contraction amount is smaller, when straightening roll-working is respectively executed at a high specific pressure than that at the time of cold roll-working to journal fillet parts 2 and pin fillet parts 4a, the fatigue strength in these fillet parts is not lowered, high dimensional accuracy is obtained because the expansion or contraction amount of the arms comes the prescribed expansion or contraction amount and also the setting work of straightening rolls is unnecessitated because the cold working roll is used as it is.