An air conditioner includes: a housing including an air inlet and an air outlet, a heat exchanger provided inside the housing, a blower fan rotatably provided inside the housing, an ultraviolet (UV) light source provided inside the housing and configured to irradiate UV light toward the blower fan, a blade rotatable, relative to the housing, configured to be in an open position for opening the air outlet or in a closed position for blocking the air outlet, and a sensor configured to detect a position of the blade, and may be configured to selectively stop operation of the UV light source based on the position of the blade detected by the sensor.