To further improve control response of valve timing by surely preventing air suction into a plunger from a hydraulic chamber.

In this internal combustion engine, a plunger 14 is installed slidably on a vane body 4 connected with a camshaft. When rotation on advance angle side is controlled, high pressure hydraulic fluid is introduced in a pressure chamber 47 in the plunger 14 through a hydraulic supply passage 59 which branches off from an upstream passage of an advance angle side hydraulic chamber 27. Consequently, an end portion of the plunger 14 is pressed against an internal face of a housing 2. A check valve 48 is provided at a hydraulic introduction portion in the plunger 14 to prevent regressive displacement of the plunger 14 by hydraulic pressure therein. Tension of the plunger 14 obtained at this stage regulates return of the vane body 4 due to torque reaction force from an engine valve. Since the hydraulic fluid is not introduced in the plunger 14 through the advance angle side hydraulic chamber 27, the air generated in the hydraulic chamber 27 is not drawn into the plunger 14.