Toothed part manufacturing method, toothed part manufacturing device, and toothed part

A toothed part manufacturing method for manufacturing a toothed part from a cylindrical blank using a forming die, wherein

• when forming a toothed portion on a radially outer section of the blank by applying a load in the axial direction of the blank to a radially center section of the blank while constraining a portion of an outer circumferential surface of the blank such that a constituent material of the blank flows radially outward, the constituent material of the blank at an intermediate section between the center section and the outer section flows in the axial direction toward a depressed portion of the forming die that is provided so as to be depressed toward opposite direction with respect to a direction in which the load is applied to form a projection portion while decreasing a constrained area of the outer circumferential surface, and
• when the load is at maximum, a space is provided between the toothed portion and the forming die, and a space is provided between the projection portion and the forming die.