An automotive air-conditioning system has a gas-liquid separator, a compressor and a radiator, which are interposed in a first flow channel of a refrigerant which extends within an engine room in the order in the flowing direction of the refrigerant. The system also includes a pressure reducer and an evaporator, which are interposed in a second flow channel of the refrigerant which extends within a vehicle interior in the order in the flowing direction of the refrigerant. The system also has a connecting device disposed near a partition wall that separates the engine room from the vehicle interior. The connecting device circularly connects the first to the second flow channel, and includes a first connecting portion formed at the downstream end of the second flow channel and a second connecting portion that is formed at the inlet of the gas-liquid separator and is connected to the first connecting portion.