PURPOSE: To obtain a lightweight cam shaft having little bending and excellent bending strength by forming a dissipation model in such a way that a metal tube is arranged into a core of a cam shaft part in casting and performing the casting using the model resulting in the obtained hollow cam shaft.

CONSTITUTION: A forming polystylene(F.P) model 10 of a cam shaft is composed of a shaft part 10a, plural cam parts and plural journal parts 10c and a stainless steel pipe 11 is arranged in the shaft core. The F.P model is placed in a mold 15 and molten metal of ductile iron is cast through a runner 17 and thus the F.P model 10 is dissipated so as to form the cam shaft with the stainless pipe 11 in the core part. By using the cam shaft with the stainless pipe buried therein, it is possible to obtain a lightweight cam shaft having little bending and excellent bending strength.