A vehicle air-conditioning system comprising: an HVAC unit that blows, into a vehicle interior, air whose temperature has been adjusted by a refrigerant evaporator and a second refrigerant condenser that are provided in a blowing path of a blower; a heat pump cycle in which a refrigerant compressor, a refrigerant circuit changeover section that changes a refrigerant circulating direction, a first refrigerant condenser that condenses refrigerant by performing heat exchange with outside air, a first expansion valve, and the refrigerant evaporator are connected in this order; a second expansion valve and a refrigerant/coolant heat exchanger are connected in parallel with the first expansion valve and the refrigerant evaporator; and the second refrigerant condenser is connected in parallel with the first refrigerant condenser via the refrigerant circuit changeover section; and a coolant cycle in which a coolant circulating pump, a motor/battery, an electric heater, and the refrigerant/coolant heat exchanger are sequentially connected; characterized in that a ventilation-exhaust-heat recovery unit that recovers heat from exhaust air from the vehicle interior is also sequentially connected in the coolant cycle to the motor/battery, the electric heater, and the refrigerant/coolant heat exchanger and in that the ventilation-exhaust-heat recovery unit, the motor/battery, and the electric heater can be selectively used as a heat source, wherein the coolant cycle comprises a first bypass circuit for bypassing the ventilation-exhaust-heat recovery unit and the motor/battery and a second bypass circuit for bypassing the ventilation-exhaust-heat recovery unit. an HVAC unit that blows, into a vehicle interior, air whose temperature has been adjusted by a refrigerant evaporator and a second refrigerant condenser that are provided in a blowing path of a blower; a heat pump cycle in which a refrigerant compressor, a refrigerant circuit changeover section that changes a refrigerant circulating direction, a first refrigerant condenser that condenses refrigerant by performing heat exchange with outside air, a first expansion valve, and the refrigerant evaporator are connected in this order; a second expansion valve and a refrigerant/coolant heat exchanger are connected in parallel with the first expansion valve and the refrigerant evaporator; and the second refrigerant condenser is connected in parallel with the first refrigerant condenser via the refrigerant circuit changeover section; and a coolant cycle in which a coolant circulating pump, a motor/battery, an electric heater, and the refrigerant/coolant heat exchanger are sequentially connected; characterized in that a ventilation-exhaust-heat recovery unit that recovers heat from exhaust air from the vehicle interior is also sequentially connected in the coolant cycle to the motor/battery, the electric heater, and the refrigerant/coolant heat exchanger and in that the ventilation-exhaust-heat recovery unit, the motor/battery, and the electric heater can be selectively used as a heat source, wherein the coolant cycle comprises a first bypass circuit for bypassing the ventilation-exhaust-heat recovery unit and the motor/battery and a second bypass circuit for bypassing the ventilation-exhaust-heat recovery unit.