A variable valve mechanism includes a first member and a second member which are disposed between a cam and a valve, a switch pin that is displaced to connect and disconnect the first member to and from the second member, and a displacement device. The displacement device includes a ring-shaped plate that is fitted on a camshaft of the cam so as to be co-rotatable with the camshaft and slidable in a longitudinal direction of the camshaft and that has one side surface configured to contact the switch pin and has the other side surface including a tapered surface formed so that a plate thickness increases toward a rotational direction, and a support device formed by a support pin and a moving device that moves the support pin to a position where the support pin contacts the tapered surface and a position not contacting the tapered surface.