A fuel-air mixture supply system comprising a Venturi portion formed on the inner surface of a cylindrical suction system having a throttle valve therein, at least one fuel injection port provided in the Venturi portion and open into the suction system, an atomizing chamber located adjacently to the fuel injection port in a co-axial manner to the fuel injection port and having a nozzle to make the atomizing chamber communicate with the fuel injection port, a fuel injection valve connected to the cylindrical suction system to inject the fuel into the atomizing chamber at a predetermined pressure and an air bleed passage making the portion above the throttle valve in the suction system communicate with the atomizing chamber. The fuel injected into the atomizing chamber from the fuel injection valve is atomized by the air drawn into the chamber from the suction system through the air bleed passage. The atomized fuel is drawn into the suction system by the air flowing on the Venturi portion and is distributed in the suction system.