PURPOSE: To prevent load from acting simultaneously upon an engine so as to heighten idling stability and the like by delaying the operation of an air- conditioning compressor only for the fixed time when the load of a power steering or the like is generated.

CONSTITUTION: A compressor 17 is cooled down and shifted into the steady state after the start of air-conditioning operation by a control unit 20, and thereafter controlled in the on-off state on the basis of signals from a temperature sensor 18 in the vehicle interior so as to maintain the internal temperature to the set value. Auxiliary machinery (a power steering pump 19 or the like) is directly driven by the rotation of an engine. When the load of the auxiliary machinery is inputted, the control unit 20 inhibits the 'on' state of the compressor 17 for the fixed short time after the input of the load so as to prevent the collapse of engine speed generated due to the input of air-conditioning load simultaneously with the load of the auxiliary machinery. Large fluctuation in the rotation of the engine generated due to the load of the auxiliary machinery acting simultaneously upon the engine is thus suppressed to enable the improvement of idling stability.