PURPOSE: To secure satisfactory control accuracy of a valve timing, simplify a whole of device, reduce its weight, improve. a manufacturing operation efficiency, and reduce a cost.

CONSTITUTION: An freely oscillatable disc housing 34 is interposed between a driving shaft 21 rotated synchronously with an engine and a cam shaft arranged coaxially therewith, while a annular disc 29 is rotatably arranged on an inner peripheral side of the disc housing 34 for interlocking the driving shaft 21 with the cam shaft 22. A control shaft 39 and an eccentric cam 45 are fitted to a bearing groove on an upper surface of a first cam bracket 38 and a cam groove 43 on an upper surface of a disc housing 34 from an upper side of the engine for oscillating the disc housing 34 through a hydraulic actuator, so as to respectively support a bearing cap 41 and a cam cap 46 in a rotatable manner.