PURPOSE: To prevent a crankshaft from being bent during working to enhance the fatigue resisting strength of the crankshaft, by changing the pressing force of the pressing roller in a part to be worked of the crankshaft.

CONSTITUTION: Pressing rollers 24 for working crank journal parts 16, 19 are all pressed under an equal pressure since no affection due to pressing force. Further, for crank pins 21, 22 which are liable to be subjected to the affection by the pressing force, the pressing forces by the pressing rollers 24 pressing the corner parts 20a, 23a of first and fourth crank pins 20, 23 positioned on both sides are set to be high, but the pressing forces of the pressing rollers 24 pressing the corner parts 21a, 22a of second and third crank pins 21, 22 positioned on the center side are set to be low during the crankshaft 15 being worked. As a result, the crankshaft 15 is not bent during working, and there are no strains in bearing slidable surfaces 16b through 19b, 20b through 23b.