PURPOSE: To prevent hunting of engine rotation and deterioration of life time of an actuator by removing output fluctuation of a generated electric current detecting means and calculating and adjusting correction quantity of the suction air sucked by an engine on the basis of the fluctuation removed generated electric current.

CONSTITUTION: Generated electric current is judged by a duty rate judged by a duty rate judgment circuit 101 on the basis of a duty signal of an alternator 1 as a generator rotated and driven by an engine and an output judgment circuit 103 on the basis of the engine speed judged by an engine speed judgment circuit 102. Because the duty rate is fluctuating, the fluctuating generated electric current is removed of its fluctuation by an electric current value fluctuation removal circuit 104 and compared with the output from the output judgment circuit 103. When the difference is less than the specified value, an averaged value is regarded as the output of the electric current value fluctuation circuit 104 but when the difference is equal to or more than the specified value, the output of the output judgment circuit 103 is outputted as it is, a suction air correction conversion circuit 105 receives this output, calculates the correction quantity of the suction air corresponding to the fluctuation quantity and corrects the bypass suction air quantity.