PURPOSE: To provide sufficient fail safe function, by providing a fully-closed position return mechanism which returns an intake air amount to a minimum when a drive signal to an actuator to control an intake air amount of an engine is disconnected, and a mechanical interlocking mechanism which effects changes in a given range.

CONSTITUTION: An actuator lever 21 is secured on a throttle shaft 25 rotated by a throttle actuator 3. An accelerator lever 20 rotated through control of an accelerator is slidably positioned in a range where the accelerator lever is prevented from corrosion with both end parts (a) and (b) of the actuator lever 21. When a throttle valve 1 is forced into an inoperable state in a fully closed state, the accelerator lever 20 is corroded with the one end part (b) of the actuator lever 21 to forcibly open the throttle valve 1. When the throttle valve 1 is forced into an inoperable state in an opened state, the accelerator level 20 is corroded with the other end part (a) of the actuator lever 21 to forcibly close the throttle valve 1.