PURPOSE: To enable to control the idling speed appropriately according to the temperature of cooling water, by effecting estimated correction of load according to the types of load and the temperature of cooling water at the time, and correcting a correction value according to the change in the engine speed at the time when estimated correction of load is executed.

CONSTITUTION: A control valve is disposed in a by-pass passage by-passing a throttle valve in an intake passage, and the control valve is so controlled by a feedback control means that the engine speed detected by an engine-speed sensor is converged to an aimed idling speed. A control apparatus of this invention comprises further a memory means which stores a correction value for correcting a feedback control value by an amount corresponding to the level of load in the manner of relating to the temperature of cooling water when output signal of a load detecting means for detecting operation of external loads such as a cooler is given to the memory means. Further, the control apparatus of this invention comprises a correction-value correcting means which increases the above correction value by a prescribed amount when the external load are operated and the engine speed is lowered resultantly and decreases the correction value by a prescribed amount when the engine speed is raised extraordinarily.