To suppress the deterioration of roundness of a shaft after forming and to prevent the deterioration of the shape of a reformed groove pattern by forging the groove pattern having a highly precise groove depth on the shaft.

By reforming the outer peripheral surface of the shaft 101 by positively pressurizing the swelling 104 in the projecting part 108 of the groove pattern which is forged on the shaft 101 by the projecting part 201 for forming the groove bottom in the circumferential direction by fitting the projecting part 108 of the groove pattern into a recessed part for reforming, the shaft 101 having the outer peripheral surface of excess metal 207 reforming the swellings 104 on both end parts of the projecting part 108 of the groove pattern is obtained. The groove depth " D1 " of the projecting part 201 for forming the groove bottom is set deeper than the quantity of the swellings 104 by material flow when the groove is forged and the bottom part 107 of the highly accurate groove pattern is forged by making the material flow of the shaft 101 free.