PROBLEM TO BE SOLVED: To cope with heavy load without being influenced by the parallelism of a driven shaft to a camshaft by forming at least one of the inner surfaces of a shaft through hole and the driven shaft inserted through the shaft through hole, into a curved surface protruded to an axial direction. SOLUTION: A cam 2 is fastened to a camshaft 1, and the camshaft l is supported in such a way as to be rotated integrally with the cam 2. A driven shaft 3 is energized in the cam face direction of the cam 2 while keeping a parallel state to the camshaft 1, and a roller follower 4 is fittingly fixed in a rotatable state to a part corresponding to the cam face of the cam 2. In the roller follower 4, the inner peripheral surface of an inner ring 4a, that is, the inner surface of a shaft through hole, and the outer peripheral surface of an outer ring 4b, that is, the contact face with the cam 2, are respectively made flat in relation to an axial direction. Even in the case of the parallelism of the driven shaft 3 to the camshaft 1 being deviated, there is no part assembled in the state of keeping the point contact relation in all directions, between the driven shaft 3 and the camshaft 1, so that heavy load can be coped with.