PURPOSE: To well execute form rolling a sylindrical part of comparatively thin wall with a few dies by treating with hardening an inner circumferential surface of this sylindrical part in advancing to the form rolling when an outer circumferential surface of the sylindrical part.

CONSTITUTION: When a bushing shaft 10 is manufactured by roll forming a knurling 14 on an outer circumferential surface of a sylindrical part, in advancing to the form rolling, an inner circumferential surface of this sylindrical part is treated with a high frequency quenching as the hardening treatment, the quenching hardness of this inner circumferential surface 14 is made to HRC 57-65. Next, the outer circumferential surface 12 is formed with rolling, the knurling 14 is formed, and this outer circumferential surface is treated with the high frequency quenching. Therefore, the form rolling with high precision can be executed.