PURPOSE: To prevent an engine from damaging, by installing a fuel-cut revolving speed decreasing device, which gradually lowers a fuel-cut revolving speed down to the lower limit value, at a time when the engine is detected as being in a racing state.

CONSTITUTION: In time of engine operation, fuel injection time is calculated on the basis of each output of a suction pressure sensor 22 and a crank angle sensor 36 at an ECU 40 and then that whether an engine speed is higher than a fuel-cut revolving speed or not is judged. When this judging result is YES and judged as necessary to cut fuel, a fuel cutting counter is counted down, and when the counting value comes to zero, successively whether an engine is in time of racing operation, smaller in the actual car speed detected by a car speed sensor 39 than the setting value (for example, 2km/hr) or not is judged. And, when YES judgment is the case, the fuel-cut revolving speed is controlled so as to be gradually lowered down to the lower limit value, and fuel-cut control is made to be performed on the basis of a newly fuel-cut revolving speed.