A cooling apparatus includes a tank for keeping a coolant liquid therein and including an air layer, a heat receiver in contact with a heat generating part for receiving heat therefrom, a radiator for radiating the heat absorbed by the coolant liquid, and a circulating mechanism for circulating the coolant liquid from the heat receiver through the tank, through the radiator and again to the heat receiver. The tank is mounted on the radiator. The radiator includes a coolant liquid circulating conduit for radiation which includes a width narrower at the middle position of the tank, and is divided by a gap at the middle position of the tank. The radiator includes cavities on both sides of a portion in which the gap in the coolant liquid circulating conduit is formed, each of the cavities having an area covered with the tank mounted on the radiator.