To provide a cam shaft easily fixing a cam piece on a drive shaft.

A cam piece combined body 3 of the cam shaft 1 is formed by combining a pair of cam piece parts 4 including cam profiles 42 as one body to align in an axial direction of the drive shaft 2. The cam piece combined bodies 3 are formed with different positions in a rotation direction. A single inner hole 31 passes through the cam piece combined body 3, and a plurality of grooves 32 extending in an insertion direction of the drive shaft 2 are formed in the inner hole 31. The drive shaft 2 is inserted in the inner hole 31 under a condition where the cam piece combined body 3 is heated and the diameter of the inner hole is expanded. An outer circumference surface of the drive shaft 2 is pressed by the inner hole 31 and rises and enter into the groove 32 by cooling the whole under the condition to contract the diameter of the inner hole 31. Consequently, the cam piece combined body 3 is firmly fixed on the drive shaft 2.