PROBLEM TO BE SOLVED: To provide an air conditioning device capable of exerting a high effect in sterilization using microplasma, and having high maintenance performance.SOLUTION: The air conditioning device including an air distribution channel 130 for sucking gas in an air conditioned space 101 to a treatment space 104 by the action of an air distributing means 103, and returning it to the air conditioned space 101 includes a microplasma generating means 6 disposed in the processing space 104, and a humidifying means 115 for humidifying the gas distributed to the microplasma generating means 6, and further includes a humidity adjusting means 116 for keeping the gas reaching the microplasma generating means 6 within an optimum humidity range to keep the sterilizing performance of the microplasma generated by the microplasma generating means 6 by humidifying the gas by the humidifying means 115.
