To considerably reduce driving load of an actuator by obtaining a large reduction ratio with preventing a transmission of alternate torque generated at working of engine to the actuator.

This device operates an intake valve for opening by oscillating an oscillation cam through a link arm, a rocker arm, and a link rod by eccentric rotation of a driving cam fixed on a driving shaft. A supporting point of oscillating of the rocker arm is changed through a control cam by controlling rotating position of a control shaft such that an amount of a valve lift of the intake valve becomes variable. Rotating drive of an electric actuator 34 which controls rotating position of the control shaft is reduced in speed by a two-stage speed reduction mechanism 40 consisting of a spur gear 43 and a worm gear 44.