To provide a cam holding mechanism that can fix a cam without using a screw for a camshaft, solve trouble following damage of the camshaft, and easily and certainly perform adjustment of a cam and fixing to the camshaft.

A fixing side member 15, a movable side member 16, and a spring 17 are arranged on a camshaft 11, a contact state between the fixing side member 15 and the movable side member 16 is changed, and a total axial size of the fixing side member 15 and the movable side member 16 is changed in length to change a pressing force of the spring 17, and a rotatable state and an unrotatable state to the camshaft 11 of each cam 12 are exchanged. Thus, a state in which a cam position can be easily adjusted and a state in which the cams 12 can be certainly fixed are smoothly switched, operability is improved, the camshaft 11 is not affected by any bad effect, and fine control of the cam 12 position can be performed without problem.