PURPOSE: To prevent a failure in control due to the slight opening of an accel and to improve the control of an idling engine speed by reducing the amount of correction of the opening of a flow control valve in the valve closing direction to set a lower guard in a pseudo manner when the opening of the flow control valve reaches a lower limit.

CONSTITUTION: An ISC valve is provided across a bypass passage for controlling an idling engine speed which bypasses a throttle valve 9 and the opening of the ISC valve 12 is controlled by an ECU 13 depending upon operation state. This constitution controls the idling engine speed to a target value after warming up completes. The target idling engine speed is calculated by the ECU 13 which enters output signals from an intake-air temperature sensor 7, a water temperature sensor 16, a throttle sensor 10, a turning angle sensor or the like In this case, when the opening of the ISC valve 12 reaches a lower limit minus a specified opening which is set based on an average opening during idling operation, it is controlled according to the amount of correction of opening which is less than the amount of control of the opening of the ISC valve before the opening reaches the lower limit.