A cooling apparatus is disclosed for cooling and dehumidifying the inside of a device such as an electronic device installed outdoors The cooling apparatus of the invention comprises a set of dehumidifying parts, each arranged at an open air intake side and an air exhaust side of a housing of the device respectively, and having filtering members for removing humidity from the open air. When air in the housing is saturated with humidity by air blowing from a fan, the rotational direction of the fan is reversed to thereby change the air flowing direction towards the dehumidification part. A dehumidification material thus receives heated and dried exhaust-air from a heating material and discharges moisture accumulated within the material to the outside, thereby recovering moisture absorption capability of the dehumidification material.