There is provided in a die a cavity for placing a powder magnetic core material, and a recessed curved surface bent inward of the die is formed at the bottom surface of the cavity. The powder magnetic core material placed in the cavity is pressed by the pressing surface of a punch to the side and bottom surfaces of the cavity to form a split tooth body. As a result, a projected curved surface having a shape following the recessed curved surface is formed on the outer peripheral surface of the split tooth body. Then, two split tooth bodies are butted and joined together at the surfaces to which pressing force by the punch is applied, and thereby a tooth is assembled.