To improve detecting accuracy of a throttle opening by correcting a throttle opening to be detected while taking an idling target opening in consideration, in a device formed in such a constitution that a throttle target opening is set so as to include the idling target opening and an accelerating target opening.

An idling speed control means 31 and an accelerating target opening setting means 32 are provided, a throttle target opening is set by a throttle target opening setting means 33 so as to include an idling target opening and an accelerating target opening which are set by each of means 31, 32, and thereby, a throttle valve 10 is opening/closing controlled. A correcting means 35 is provided so as to correct a throttle opening detected by a throttle opening detecting means 34 taking the idling target opening in consideration, the idling target opening is subtracted from the throttle opening to be detected, and thereby, it is possible to prevent the throttle opening from fluctuating if a load is fluctuated by means of turning on/off of an air conditioner.