PURPOSE: To improve the response under acceleration and to prevent excessive fuel supply under deceleration, by performing the fuel injection on the basis of the varying operating condition of engine such that the fuel is injected to a plurality of cylinders corresponding to a single cylinder signal during acceleration while the fuel injection is thinned out during deceleration.

CONSTITUTION: When an engine is operating, a control unit 2 corrects a basic injection quantity Tp obtained on the basis of the outputs from a crank angle sensor 1 and an air flow meter 4 according to the outputs from a water temperature sensor 5, etc. so as to set a fuel injection quantity Ti. Then the varying condition of operation is detected, and if it is decided that the engine is operating under steady state, fuel injection is performed for the fuel injection valve 11 of next cylinder on the basis of the fuel injection quantity Ti. While when it is decided that the engine is transferred to an accelerating operation, fuel is injected from fuel injection valves 11 of a plurality of cylinders. When it is decided that the engine is transferred to a decelerating operation, fuel injection is thinned out.