A rotational cam can be disposed on a camshaft rotationally driven by a crankshaft of an internal combustion engine. A swing cam can be swingable through the rotational cam. The swing cam has a rotational cam abutment portion which contacts the rotational cam and transmits driving force from the rotational cam to the swing cam. An abutment portion displacing mechanism can be provided for displacing the rotational cam abutment portion to change a relative distance between the rotational cam abutment portion and a center axis of the swing shaft. Changing the relative distance allows changing a lift and the like of a valve.