To appropriately control a feeding air-fuel ratio from immediately after starting and a completion explosion.

A behavior characteristic of an engine revolution number at the time when a feeding air-fuel ratio is appropriately controlled from immediately after starting and a complete explosion is previously determined by an experiment or a simulation and is memorized at a map or a numerical formula as a behavior characteristic of the target engine revolution number TNe. A first injection correction amount al is calculated corresponding to a deviation of an actual engine revolution number Ne after the complete explosion and the target engine revolution number TNe and a second injection correction amount a2 is calculated corresponding to a deviation of a future engine revolution number presumed from a suction air amount and the target engine revolution number TNe. Further, the injection correction amount (a1+a2) is corrected with a correction coefficient b calculated corresponding to an integration value IntFAD of a combustion unstability degree to determine a final injection correction amount a. A feeding air-fuel ratio after the complete explosion is controlled by correcting the fuel injection amount using the final injection correction amount a such that the actual engine revolution number after the complete explosion is converged to the target engine revolution number TNe.