Abstract: An air cutoff valve (ACV) is provided. The full open state of the flap valve is maintained using the latchet which operates as the solenoid is turned on and off, so the restart performance is significantly enhanced as the air is quickly supplied by the ACV when the engine stops abnormally irrespective of a driver's intention, and since the ACV is made from a plastic material, the assembling process of the molding formation is simplified, so the unit cost for manufactures is reduced, and the corrosion phenomenon due to moisture can be prevented, and the operation reliability can be enhanced.