An air-conditioning system for a vehicle having an engine adapted to stop idling on predetermined stop conditions of the vehicle, which system comprises an electric motor for driving a refrigerant compressor when the engine idling is stopped, motor speed control means for controlling the speed of the motor in correspondence with an evaporator outlet temperature, and evaporator temperature correction means for, when the engine idling is stopped while outside air is being introduced, correcting the evaporator outlet temperature to a lower temperature in correspondence with a temperature of the outside air and a temperature of engine cooling water.