On one side of a valve shaft, there are provided an accelerator drum connected to an accelerator pedal by an accelerator wire, a return spring for urging the accelerator drum in a valve closing direction, and an accelerator sensor for detecting rotation of the accelerator drum and transmitting a detected signal to a host system. On the other side of the valve shaft, there are provided a large-diameter gear and an opening sensor. An armature of a solenoid clutch is attached to the gear and held on a motor shaft via a slide bearing. Thus, the motor, the solenoid clutch and the throttle valve are arranged into a U-shaped form for interconnection through four gears.