PURPOSE: To exhibit a dashpot function properly by controlling driving of a motor for valve switching so as not to close a throttle valve smaller than a target opening degree at decelerating after a prescribed waiting time has passed from the operating start of at least either of accelerating or decelerating.

CONSTITUTION: An idle switch 18 which detects whether or not an internal combustion engine 2 is in an idle driving and turns on and off is provided. Besides, a motor for valve driving 16 which controls switching of a throttle valve 8 at the time of particular driving of the internal combustion engine 2 is provided. With this constitution, a control means 20 controls driving of the motor for valve switching 16 so as not to close the throttle valve 8 smaller than a target opening degree at decelerating after a prescribed siting time has passed from the operating start of at least either of accelerating driving or decelerating driving. At the time of decelerating driving, the throttle valve 8 is open larger than the target opening degree at decelerating, so it is possible to exhibit the dashpot function properly.