Abstract: An air conditioner for a coating booth is constructed so as to intake the air through a filter for eliminating dust, to heat the air by a plate fin coil heater to the extent that it is not excessively saturated, to atomize the steam directly into the air via a steam atomizing tube, to contact the air including the atomized steam with water flowing down on the surfaces of the wet walls, to make the recirculating water absorb the steam for giving energy for humidifying to the water, to humidify the air by contacting the flowing water and to feed the humidified air through an eliminator to a coating booth at a temperature controlled by another plate fin coil heater.