PURPOSE: To reduce an air-fuel ratio change amount when inference is ma de as an air-fuel ratio feedback control correction coefficient for another operation state on the basis of the outcome of air fuel ratio which feedback control having been done, by using a map which has made a value that has reduced a correction amount according to the increase of an intake air amount, a learning value.

CONSTITUTION: At a control unit 15, when it is decided from the output of a water temperature sensor 20 that the state of air-fuel ratio feedback control being possible exists, a fuel injection pulse width is calculated from the output of an air flow sensor 3 and a crank angle sensor 16. I And the correction of a fuel injection pulse width value is made by multiplying its calculated value by an air fuel ratio feedback control coefficient ALPM based on an air-fuel ratio sensor 19, and an injecter 13 is drivingly controlled. In this case, at a data housing map seeking the ALPM an arrangement is made so that a value which has multiplied the ALPM by a fixed reduction correction coefficient may be housed as a learning value at a map lattice point housing portion whose specification becomes larger than an air amount at a point to which the ALPM in a free operation state is applicable.