PURPOSE: To prevent erroneous learning of an air-fuel ratio learning correction value and improve emission and drivability by learning an air-fuel ratio learning correction value and an intake air temperature correction value at a fuel injection time under different temperature conditions and correcting a fuel injection time in response to respective correction values.

CONSTITUTION: The fuel injection valve 5 of an engine 100 is controlled by an electronic controller 6 based on respective detection signals from at least an intake pressure sensor 13 or a rotational speed sensor 14, Namely, an air- fuel ratio learning correction value for calculating the fuel injection time in response to an operational condition of the engine 100 is learnt by the electronic controller 6, and also the fuel injection time is corrected by at least an intake temperature correction value and an air-fuel ratio learning correction vale in response to the detected intake air temperature In this case, when the detected intake air temperature under an engine load is outside a set temperature range, learning of the intake air temperature correction value is performed. On the other hand, the air fuel ratio learning correction value is learnt only within a set temperature range.