A vehicle air-conditioning system comprising: inside-outside air switching means for switching between an inside air recirculation mode to take in air from an inside air introduction port and an outside air introduction mode to take in air from an outside air introduction port; blowing means for blowing the air introduced through any of the inside air introduction port and the outside air introduction port toward inside of a vehicle cabin; heating means for heating the air blown by the blowing means; air-conditioning controlling means for activating the heating means when there is a request for heating the inside of the vehicle cabin; preliminary air-conditioning controlling means for performing preliminary air-conditioning in which air conditioning is controlled such that an environment inside the vehicle cabin becomes a desired environment by set estimated time of departure; inside-outside air switching controlling means for controlling the inside-outside air switching means when there is the request for heating the inside of the vehicle cabin in the preliminary air conditioning, in such a way as to alternately switch between the inside air recirculation mode for a first predetermined time period and the outside air introduction mode for a second predetermined time period; and cooling means including an interior heat exchanger for cooling the air blown by the blowing means and a compressor for compressing a coolant after heat-exchange in the interior heat exchanger, characterized in that the inside-outside air switching controlling means performs an operation in the outside air introduction mode for the second predetermined time period when the compressor is operated during the preliminary air conditioning, and performs an operation in the inside air recirculation mode for the second predetermined time period when the compressor is not operated during the preliminary air conditioning. inside-outside air switching means for switching between an inside air recirculation mode to take in air from an inside air introduction port and an outside air introduction mode to take in air from an outside air introduction port; blowing means for blowing the air introduced through any of the inside air introduction port and the outside air introduction port toward inside of a vehicle cabin; heating means for heating the air blown by the blowing means; air-conditioning controlling means for activating the heating means when there is a request for heating the inside of the vehicle cabin; preliminary air-conditioning controlling means for performing preliminary air-conditioning in which air conditioning is controlled such that an environment inside the vehicle cabin becomes a desired environment by set estimated time of departure; inside-outside air switching controlling means for controlling the inside-outside air switching means when there is the request for heating the inside of the vehicle cabin in the preliminary air conditioning, in such a way as to alternately switch between the inside air recirculation mode for a first predetermined time period and the outside air introduction mode for a second predetermined time period; and cooling means including an interior heat exchanger for cooling the air blown by the blowing means and a compressor for compressing a coolant after heat-exchange in the interior heat exchanger, characterized in that the inside-outside air switching controlling means performs an operation in the outside air introduction mode for the second predetermined time period when the compressor is operated during the preliminary air conditioning, and performs an operation in the inside air recirculation mode for the second predetermined time period when the compressor is not operated during the preliminary air conditioning.