A humidity control device of an air conditioner having an air conditioner body and being capable of controlling a humidity as well as conditioning air during heating, drying and like operations, comprises a target humidity setting unit for setting a target humidity in accordance with operation modes, a humidity sensor for detecting a humidity in a room, a humidity setting element for setting a humidity in the room, a control unit for comparing the humidity detected by the humidity detecting element with the humidity set by the humidity setting unit and controlling the compared humidity, and a humidifier responsive to the control unit to receive an operation command signal from the control unit in accordance with the detected and set humidities to thereby control the humidity in the room. The humidifier is arranged independently from the air conditioner body and the control unit transmits a humidifier control signal to the humidifier through a wireless transmission. A controller is further provided for controlling the air conditioner and a remote controller for controlling the operation of the controller is also provided.