PURPOSE: To obtain a mixture of a predetermined air-fuel ratio with a necessary and minimum amount of fuel by a method wherein a correction pulse signal corresponding to operation parameters is generated for a certain time period at the start of the engine.

CONSTITUTION: In a central control and operation part 8 which receives signals from an intake air amount sensor 4 provided upstream the throttle valve 5 of an internal combustion engine 1, a pressure sensor 7 provided downstream the throttle valve 5 and an engine speed sensor 12, etc., and outputs a signal to control a fuel injection valve 6 through a drive circuit 9, it is first discriminated whether the engine 1 is starting or not based on the input information from the sensors 4, 7 and the like, and in case of starting of the engine 1, correction pulse width, correction pulse generation time period and reference pulse width are calculated in accordance with the input information, and further, if there is an interruption from the sensor 12, a reference pulse is outputted, and additionally, a correction pulse of a predetermined width is outputted after a certain time delay on the starting of the engine 1. By this method, the fuel injection valve 6 is opened not only by the reference pulse but also by the correction pulse, thereby obtaining an appropriate air-fuel ratio at the engine start.