an estimating execution for an inner surface portion adhesion fuel amount is practiced distinctlly and independently to an execution processing for a basic fuel injection amount . a correction coefficient to be multiplied by the basic fuel injection amount is calculated in accordance with the estimation execution for the inner wall surface portion adhesion fuel amount . the correction coefficient is multiplied by the basic fuel injection amount . since the fuel injection amount is corrected in accordance with the estimated inner surface portion adhesion fuel amount , an air - fuel ratio during a transitional period of an engine can be maintained at a desirable value .