The cooling apparatus comprises an air supply system, a water supply system, and a sprayer, and has a structure such that water and compressed air are mixed and the air is sprayed together with the water converted into mist onto the upper surface of a device attached to a socket of a burn-in board. The amount of heat generated by the device that generates a large amount of heat is removed via the heat including a large latent heat when the mist that falls on the upper surface is evaporated, and the burn-in is conducted, while the device is being cooled to the target temperature.