PURPOSE: To produce a cam shaft including cast-in piece having high joining strength at low cost by sinter-joining the piece and cast iron through a sintering furnace after inserting the piece composed of green compact, etc., for sintering alloy as the cast-in with the cast iron for forming shaft.

CONSTITUTION: Cam lobe or piece for forming a journal composed of the green compact for the sintering alloy or provisional sintered body or regular sintered body is inserted with the cast iron for forming the shaft as the cast-in. By this method, boundary part between the piece and the cast iron is made to alloy and both is firmly joined. After that, by passing the cast-in body through the sintering furnace, the piece and the cast iron are sinter-joined. By this sintering, diffusion of elements is developed at the joined part and the joined strength is further improved. Further, in case the above piece is the green compact or the provisional sintered body, as it is shrunk with the sintering to tighten up the cast iron-made shaft, particularly the firm joining is executed. By this method, the cam shaft having high joined strength between the piece and the shaft and high reliability, is obtd.