In a variable valve timing mechanism, a valve-lifting cam member is fitted, slidably in tile circumferential direction, onto a camshaft that is driven to rotate in synchronization with a crankshaft of a four-stroke cycle internal combustion engine. An eccentric collar is set between a driving collar fixed on the camshaft and the valve-lifting cam member. A driving projection is formed in the driving collar and engages with one of sandwiching portions of the eccentric collar. A driven protrusion is formed in the valve-lifting cam member and engages with another one of the sandwiching portions of the eccentric collar. A linkage mechanism includes the eccentric collar, the drive, and the driven protrusions. The variable valve timing mechanism adjusts the timing of opening and closing of the valve while the rotational phase of the valve-lifting cam member is cyclically varied relative to the camshaft by the eccentricity of the eccentric collar.