PURPOSE: To both simplify construction and perform cost down of a valve driving gear, in a valve recess device of an internal combustion engine, by providing a check valve control mechanism in which a check valve, limiting a discharge of oil from a pressure receiving chamber, is released to perform a valve recess.

CONSTITUTION: A valve driving gear is equipped with a cam 9 and cam follower 6. When an opening and closing valve 3 is operated to a recess state, a solenoid 24 is excited to insert a control plunger 25 into a nozzle 18 and open a check valve 19. Under this condition, pressure oil in a pressure receiving chamber 11 is discharged from a hydraulic pressure discharge port 17 via the nozzle 18, buffer chamber 22 and discharge port 23, then a plunger 7 can not be supported. In consequence, the piston plunger 7 is sunk in a cylinder 10, and the opening and closing valve 3 is placed to a recess condition. In this way, construction of the valve driving gear with a valve recess function can be simplified to form the driving gear to small size and reduce its cost.