PURPOSE: To obtain an air cooling with a simple structure by supplying into a room a cooling air obtained by impregnating sand and gravel which absorb the geothermal energy in the ground with tap water.

CONSTITUTION: Two sets of vessels 1, 5, 2 and 3, 5, 4 are provided for suctioning external air and changing the same into primary and secondary cooling airs. The vessel 5 of each set contains the sand and gravel 12 which absorbs the geothermal energy. In order to obtain a more effective cooling air, a water supply plug 8 is connected to the bottom of the vessel 1. The two sets of vessels are interconnected via an air channel 6, an air feeder 7 and a water conduit 10. The secondary cooling air heat-exchanged by the second set of vessels 3, 5, 4 is supplied through a pipe 6 to an air blowing outlet 13 provided at the respective room.