An air conditioner including a heat exchanger (16), a drain pan (22) for receiving drain water generated in the heat exchanger (16), a drain pump (12) for pumping drain water stocked in the drain pan (22) and discharging the pumped drain water through a drain hose (19) to the outside, and an electrolyzing unit (30, 50) having an electrode (32, 33, 52, 53) for electrolyzing the drain water and generating active oxygen species that is disposed at at least one of a suction port and a discharge port of the drain pump (12), the drain water thus electrolyzed by the electrolyzing unit being returned to the drain pan again.