To provide a switch device of a car air conditioner, which urges a user to accurately understand functions thereof.

The switch device of the car air conditioner includes a switch 20 which is operated to designate a control mode to an ECU 8 that controls air conditioning of a vehicle interior. The switch device of the car air conditioner is provided with a liquid crystal screen 11 that can be switched to a display mode showing a specified function exhibited in accordance with the control mode of the ECU 8 instructed through the operation of the switch 20.