PURPOSE: To prevent a delay response at the time of change-over of control by providing a region correcting solenoid valve for opening and closing an air or a fuel passage provided separately from a passage on which an air-fuel ratio correcting means is arranged and feedforward-controlling the air-fuel ratio correcting means by an amount correcting a varied amount of an air-fuel ratio resulted from opening and closing this valve.

CONSTITUTION: A feedback carburetor is provided with an electronic control unit 11 which controls an air-fuel ratio correcting means 9 of the carburetor so as to bring an air-fuel ratio of a mixture close to the stoichiometric air-fuel ratio corresponding to output of an oxygen sensor 12 installed in an exhaust system for the air-fuel ratio detection. A region correcting solenoid valve 18 is hereupon installed for opening and closing an air or a fuel passage 17 provided separately from a passage 10 on which the air-fuel ratio correcting means 9 is arranged. When the air-fuel ratio correcting means 9 is out from an ordinary use region, the solenoid valve 18 is opened or closed to expand a region of the air-fuel ratio and simultaneously the air-fuel ratio correcting means 9 is feedforward-controlled by an amount to correct a varied amount of the air-fuel ratio resulted from opening or closing the region correcting solenoid valve 18.