In forming an internal gear from a blank (2) for the internal gear, first the blank (2) is fitted on a form (3) and fixed thereon by a press form (4). Then, a forming roll (5) is moved in the direction of arrow (B) in Fig. 6 while rotating the form (3). This presses the inner peripheral surface of the blank (1) against an external gear section (3b) formed on the outer peripheral surface of the form (3) to form an internal gear section (1c) in the inner peripheral surface of the blank (2). The direction of rotation of the form (3) is selected such that the end of an external gear section (3b) positioned forwardly of the direction of feed of the forming roll (5) precedes the end positioned rearwardly of the direction of feed as seen in the direction of rotation of the form (3). (That is, the direction of arrow (A) in Fig. 6 is selected.)