A carburetor with a single fuel system that is capable of ensuring stable engine operation and lower fuel consumption. The fuel system comprises an electrical fuel control C that, in addition to mechanically coordinating the fuel flow rate with air intake by way of a metering needle 22 that operates in coordination with the throttle valve 3, opens and closes opening/closing valve 30 and cuts off and delivers fuel to the air intake passage 2 so as to maintain a required target rotational speed with little fuel consumption in a specific region of the degrees of opening of the throttle valve 3. Stable operation with minimal fluctuations in the rotational speed is ensured by cutting off the fuel when the rotational speed rises above the target rotational speed, and delivering the fuel when the rotational speed falls below the target rotational speed.