To increase the mechanical durability of a slit part while enlarging the pressure receiving area of the slit part by fastening a cylindrical member to an end of a cylindrical shaft member over the diameter thereof with pipe enlarging method, and providing this cylindrical member fastened part with a slit for driving a pump or the like.

Cam lobes 21, 22 and a cylindrical member 31 are fastened to a hollow shaft 1 as a shaft member by the pipe enlarging method, and the cylindrical member 31 and the hollow shaft 1 are formed with a slit 4 by milling the hollow shaft 1 and the cylindrical member 31 after fastening the cylindrical member 31 to the hollow shaft 1. Or, before fastening the cylindrical member 31 to the hollow shaft 1, a slit can be previously formed in the hollow shaft 1 and the cylindrical member 31, and thereafter, the hollow shaft 1 and the cylindrical member 31 are fastened to each other so as to form the slit 4. With this structure, thickness of the slit part can be increased, and an assembling type cam shaft for engine having high mechanical durability can be easily manufactured.