NOVELTY - The system (1) has a heat exchanger (14) for carrying out heat exchange between refrigerant and air-conditioning air. A cooling portion (30) cools a heat generation source using the refrigerant to flow between another heat exchanger (15) and a pressure reducer. A gas-liquid separator (40) separates the refrigerant into liquid-phase refrigerant and gas-phase refrigerant that flows between the former exchanger and the cooling portion. A liquid accumulator (74) is provided between the separator and the cooling portion, and retains the liquid-phase refrigerant separated by the separator.    USE - System for cooling a heat generation source e.g. electric apparatus such as motor, generator, inverter and secondary battery e.g. lithium-ion battery and nickel hydride battery, of a vehicle i.e. hybrid vehicle. Can also be used for a fuel cell-powered vehicle and an electric vehicle.    ADVANTAGE - The system ensures the refrigerant in a liquid phase state to be flowed to the heat generation source at certain flow rate, so that the system can restrain capacity to cool the heat generation source from deteriorating and can stably cool the heat generation source. The system can reduce power consumption of a compressor to improve fuel economy of the vehicle without operating the compressor to cool the electric apparatus of the vehicle, so that the cooling system can enhance reliability of the compressor due to life of the compressor can be prolonged. The gas-liquid separator can reliably separate the gas-phase refrigerant and the liquid-phase refrigerant from each other due to refrigerant vapors.    DETAILED DESCRIPTION - The heat generation source is an electric apparatus (31). The pressure reducer is an expansion valve (16).    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a system for cooling a heat generation source of a vehicle.    System for cooling heat generation source of vehicle (1)    Vapor compression refrigeration cycle (10)    Heat exchangers (14, 15, 18)    Cooling portion (30)    Electric apparatus (31)    Gas-liquid separator (40)    Liquid accumulator (74)