PURPOSE: To obtain a product, of which the cam faces of cam parts are formed with good accuracy, by fixing a preformed working reference member to a core and executing insert casting in a main mold so that the working reference member is partly projected to the outside periphery of a hollow cam shaft after casting.

CONSTITUTION: The working reference member 1 consisting of a cylindrical part 1a, a supporting column part 1b, and a supporting part 1c is fixed to a core 2 having a circular cylindical shape; thereafter, the supporting part 1c is engaged with a recess 3b of a drag 3 and the core 2 is set in the master mold 3. The insert casting is executed wit the member 1 as a chaplet so that the supporting part 1c is projected to the outside circumference of a hollow cam shaft 4 after casting at the time of casting. The cam faces 4c of the cam shaft 4 are thereby finished to good accuracy and the product is obtd. after the supporting part 1c is removed. The hollow cam shaft formed with the cam faces of the cam parts with good accuracy is thereby produced.