Provided is an air conditioner. The air conditioner includes a humidification medium, a watering housing to spray water to supply moisture to the humidification medium, a watering motor to rotate the watering housing, a blower fan to blow air, a blower motor to rotate the blower fan, an operation module receiving an instruction from a user, a sterilization module to sterilize the humidification medium, and a control unit to control the watering motor, the blower motor, and the sterilization module according to an instruction inputted to the operation module. Herein, the control unit stops an operation of the watering motor according to the instruction inputted to the operation module, operates the blower motor and the sterilization module when the sterilizing dry mode is set, and stops the operation of the sterilization module after a predetermined sterilizing dry time elapses.