PURPOSE: To surely supply assist air to each fuel injection valve without depending on an opening of a throttle valve while forming an air compressor to be compact and power-saving for an internal combustion engine having an air assist type fuel injection device.

CONSTITUTION: An air control valve 100 for distributing pressure air from an air compression synchronously with rotation of an engine is provided. A suction air port 7 for taking the pressure air from the air compressor, and a discharge port 8 connected to each fuel injection valve are provided. A rotor 6 to rotate with the engine is provided inside, and an aperture 11 is formed for a predetermined angular range in the rotor 6. The aperture 11 connects the suction port 7 to the discharge port 8 by rotation of the rotor 6. Assist air is thus supplied to each fuel injection valve in order.