There is provided a variable valve timing system for an engine in which a cylinder head is fixed on a cylinder, and the cylinder head is suspended on a vehicle body frame, the variable valve timing system including: a variable valve device configured to change an opening and closing timing of a valve according to a hydraulic pressure; and an oil control valve. The vehicle body frame includes a main frame configured to laterally cover a rear side of the cylinder head and a down frame configured to laterally cover a front side of the cylinder head. In a side view of a vehicle, the oil control valve is detachably disposed on an outer surface of the engine below an area surrounded by the main frame, the down frame, and a lower surface of the cylinder head.