Disclosed herein is a continuously variable valve lift system for an engine which is able to variably adjust valve lift and opening duration of intake and exhaust valves operated by the rotation of a cam shaft. The continuously variable valve lift system of the present invention has a compact structure, so that space required for the system in a cylinder head is reduced. Furthermore, the continuously variable valve lift system is provided at a position level with or below a position at which the cam shaft is installed, thus reducing the overall height of the cylinder head, thereby reducing the volume of the engine.