PURPOSE: To prevent the rotation change at the idling time by an electric load by calculating the drive amount of a magnetized coil by comparing a target voltage for generating with a voltage of a condensing means and controlling the drive amount of ISC valve by adding the drive amount of the magnetized coil and an electric load correction amount.

CONSTITUTION: During an engine running, a basic pulse range is calculated based on the outputs of a throttle sensor 1, a water temperature sensor 3 and a crack angle sensor 7 and a basic advance angle is calculated after an advance angle map reference in a control unit 71. Then, a target number of revolution is map refered based on the water temperature and the difference between the target number of revolution and an actual number of revolution is found out and ISC drive amount is calculated. While, a target generating voltage is calculated based on a battery temperature and also the deviation of the battery voltage for a target value is calculated and the magnetized coil drive amount of a generator 51 is found out from this deviation. The ISC correction amount is calculated from this magnetized coil drive amount and ISC valve 41 is controlled by this and a control amount added to the ISC drive amount.