To provide compatibility of miniaturization of a cooling system and cooling performance, in a cooling device for a hybrid electric vehicle.

A water jacket J2 of an inverter and water jackets J3, J4 of a generator 2 and an electric motor 3 are piped in parallel with a radiator 14 for an electric system, having cooling fans 29, 30, so as to circulate a refrigerant to an electric pump 15. A variable throttle valve 22 is provided on the inlet side of the water jacket J2 provided on an inverter module 4. A controller 28 is provided for controlling the variable throttle valve 22, so as that the temperature becomes the saturation temperature of the refrigerant, when heat load of the inverter 4 is large, whereas for controlling the operation of the cooling fans 29, 30 is controlled, so as to make a specified value or less as a value lower than the saturation temperature of the refrigerant, when heat load is small.