An air-conditioning system comprising: a first refrigerant circuit configured to circulate therein a first refrigerant, the first refrigerant circuit including a first outdoor unit and an indoor unit; and a second refrigerant circuit configured to circulate therein a second refrigerant, the second refrigerant circuit including a second outdoor unit and a ventilator, the first refrigerant circuit including a first compressor, a first outdoor heat exchanger, a first expansion valve, and an indoor heat exchanger, the second refrigerant circuit including a second compressor, a second outdoor heat exchanger, a second expansion valve, and a cooler, the first outdoor unit including the first compressor and the first outdoor heat exchanger, the second outdoor unit including the second compressor and the second outdoor heat exchanger, the indoor unit including the first expansion valve and the indoor heat exchanger, and being configured to circulate indoor air while controlling a temperature of the indoor air, the ventilator including the second expansion valve and the cooler, and being configured to exchange the indoor air and the outdoor air and control a temperature of the exchanged indoor air and outdoor air, the first outdoor unit being connected to the indoor unit by refrigerant piping (104, 105), the second outdoor unit being connected to the ventilator by refrigerant piping (104, 105), the air-conditioning system further including a unit configured to detect a temperature and a humidity of the outdoor air, wherein the air-conditioning system is configured to determine an evaporating temperature control range for the first refrigerant circuit, based on the temperature of the outdoor air, control an evaporating temperature of the first refrigerant circuit to a target evaporating temperature determined within the evaporating temperature control range for the first refrigerant circuit, determine an evaporating temperature control range for the second refrigerant circuit determined based on the humidity of the outdoor air, and control an evaporating temperature of the second refrigerant circuit to a target evaporating temperature determined within the evaporating temperature control range for the second refrigerant circuit. a first refrigerant circuit configured to circulate therein a first refrigerant, the first refrigerant circuit including a first outdoor unit and an indoor unit; and a second refrigerant circuit configured to circulate therein a second refrigerant, the second refrigerant circuit including a second outdoor unit and a ventilator, the first refrigerant circuit including a first compressor, a first outdoor heat exchanger, a first expansion valve, and an indoor heat exchanger, the second refrigerant circuit including a second compressor, a second outdoor heat exchanger, a second expansion valve, and a cooler, the first outdoor unit including the first compressor and the first outdoor heat exchanger, the second outdoor unit including the second compressor and the second outdoor heat exchanger, the indoor unit including the first expansion valve and the indoor heat exchanger, and being configured to circulate indoor air while controlling a temperature of the indoor air, the ventilator including the second expansion valve and the cooler, and being configured to exchange the indoor air and the outdoor air and control a temperature of the exchanged indoor air and outdoor air, the first outdoor unit including the first compressor and the first outdoor heat exchanger, the second outdoor unit including the second compressor and the second outdoor heat exchanger, the indoor unit including the first expansion valve and the indoor heat exchanger, and being configured to circulate indoor air while controlling a temperature of the indoor air, the ventilator including the second expansion valve and the cooler, and being configured to exchange the indoor air and the outdoor air and control a temperature of the exchanged indoor air and outdoor air, the first outdoor unit being connected to the indoor unit by refrigerant piping (104, 105), the second outdoor unit being connected to the ventilator by refrigerant piping (104, 105), the air-conditioning system further including a unit configured to detect a temperature and a humidity of the outdoor air, wherein the air-conditioning system is configured to determine an evaporating temperature control range for the first refrigerant circuit, based on the temperature of the outdoor air, control an evaporating temperature of the first refrigerant circuit to a target evaporating temperature determined within the evaporating temperature control range for the first refrigerant circuit, determine an evaporating temperature control range for the second refrigerant circuit determined based on the humidity of the outdoor air, and control an evaporating temperature of the second refrigerant circuit to a target evaporating temperature determined within the evaporating temperature control range for the second refrigerant circuit.