A cooling device has a case defining a first space through which a first fluid flows and a second space through which a second fluid having the temperature lower than that of the first fluid flows. A first heat exchanger is disposed in the first space for performing heat exchange between the first fluid and a refrigerant, thereby to evaporate the refrigerant. A second heat exchanger is disposed in the second space for performing heat exchange between the second fluid and the refrigerant evaporated in the first heat exchanger, thereby to transfer heat of the refrigerant to the second fluid. The case defines a first dimension in a first direction and a second dimension in a second direction perpendicular to the first direction in a transverse cross-section. The second dimension is larger than the first dimension. The first space and the second space are arranged in the second direction.