PURPOSE: To provide the remelt hardening treatment method, in which manufacturing process of e.g. cam shaft for engine parts can be simplified.

CONSTITUTION: Molten metal is poured into cavity in dies, and at the time, when surface layer of the molten metal becomes shell-like solidified layer, the dies are opened and the cam shaft raw material is formed while avoiding hot tear, etc. Then, to the position needing wear resistance, such as cam part in the raw material, remelt is directly and locally executed without applying surface work, such as grinding work, and high hardness metal powder, such as nickel, is added to execute the hardening treatment. By this method, dimensional accuracy and surface roughness of the raw material are improved with the die casting and further, as impurity, such as oxide, is not contained on the surface, the process of grinding work can be saved and as the remelting treatment utilizing the remaining casting heat can be executed, this manufacturing process is efficient.