There is provided a variable valve timing system, including: a camshaft rotatably supported by a support wall of an engine; a variable valve device configured to advance or retard the camshaft by a hydraulic pressure; and an oil control valve. A thrust stopper is formed on an outer peripheral surface of the camshaft. A bearing surface of the support wall is formed with an advance groove through which oil for advancing the camshaft is to pass, a retard groove through which oil for retarding the camshaft is to pass, and an accommodation groove configured to accommodate the thrust stopper. At the bearing surface, the retard groove is positioned on one wall surface side of the support wall, the accommodation groove is positioned on the other wall surface side of the support wall, and the advance groove is positioned between the retard groove and the accommodation groove.