Abstract: A carburetor comprises an intake passage for supplying air and fuel, a venturi located in the intake passage, a nozzle opened in the venturi, a float member communicated with a fuel supply source and with the nozzle, an air vent for communicating the space above the liquid surface in the float chamber with the intake passage upstream of the venturi, and two communication conduits each of which has one end opened above the liquid surface in the float chamber and the other end opened at a suitable position in the intake passage in such a manner that a pressure difference is caused between the two communication conduits. One end of the first communication means is provided close to a fuel opening connected to the fuel supply source in the float chamber and the other end thereof receives higher pressure. One end of the second communication means is provided far from the fuel opening and the other end thereof receives lower pressure.