To reduce setting manhour of an excessive fuel injection correcting rate.

By a control unit 10, a fuel injection rate is calculated according to an engine operating condition, and is injected from a fuel injection valve 7 to an engine. In the control unit 10, at the time of engine excessive operation, a fuel injection excessive correcting rate is calculated according to a fluctuation condition of a real engine air-fuel ratio detected by an air-fuel ratio sensor 13 for outputting a signal corresponding to 1:1 to an exhaust air-fuel ratio, which is arranged in an exhaust passage of the engine, for example, corresponding to a peak value of air-fuel ratio fluctuation. Since an excessive correcting rate is calculated on the basis of the air-fuel ratio fluctuation at the time of real excessive operation, various kinds of cases is imagined beforehand, and setting of the excessive correcting rate is eliminated so as to sharply reduce manhour for setting.