NOVELTY - The apparatus (1) has a pressure reducer reducing pressure of a refrigerant. A heat exchanger (14) performs heat exchange between the refrigerant and air-conditioning air. A cooling unit (30) is provided on a path of the refrigerant extending between another heat exchanger (18) and the former heat exchanger via the pressure reducer to cool a heat generation source i.e. hybrid vehicle device (31), by using the refrigerant. A four-way valve (28) switches between refrigerant flow from a compressor (12) to the latter exchanger and refrigerant flow from the compressor to the former exchanger.    USE - Cooling apparatus i.e. vehicle-installed cooling apparatus, for cooling a heat generation source i.e. hybrid vehicle device, by using a vapor compression refrigeration cycle for cooling a passenger compartment of a vehicle e.g. hybrid vehicle, fuel cell vehicle and electric automobile, installed with an electric device e.g. motor/generator and inverter.    ADVANTAGE - The former heat exchanger is provided with ability to cool the refrigerant sufficiently, so that radiation capacity of the former heat exchanger for discharging the heat from the refrigerant improves beyond radiation capacity of the latter heat exchanger. The apparatus utilizes a damper that is operated to set an air-conditioning air path through a duct such that the air-conditioning air passes through a heater core, thus utilizing waste heat from an engine for heating and heating the passenger compartment of the vehicle efficiently, and hence improving heating ability. The apparatus sets the hybrid vehicle device as a heat pipe heating portion and a cooling passage as a heat pipe cooling portion, so that heat transfer efficiency between the cooling passage and the hybrid vehicle device can be improved. The apparatus causes an amount of the refrigerant required to cool the hybrid vehicle device in the cooling unit to flow to refrigerant passages, so that the hybrid vehicle device is cooled appropriately, thus preventing overcooling of the hybrid vehicle device in a cost effective manner. The apparatus avoids need to provide the two heat exchangers to exchange the heat with the air-conditioning air, thus achieving reductions in cost and size of the apparatus.    DETAILED DESCRIPTION - The refrigerant is a high-temperature and high-pressure gas phase refrigerant and a high-pressure liquid phase refrigerant.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a cooling apparatus.    Cooling apparatus (1)    Compressor (12)    Heat exchangers (14, 18)    Four-way valve (28)    Cooling unit (30)    Hybrid vehicle device (31)