To provide a controller of an air conditioner enabling the convenience in changing set values to be enhanced.

This controller (remote controller) 1 of an air conditioner A is operated in different settable ranges according to a plurality of operating functions. The controller comprises a display means 6 for displaying settable upper and lower limit values, a set value, and a present value and a control means 3 for storing the settable ranges and displaying the upper and lower limit values based on the settable ranges according to the operating conditions of the air conditioner. The display means 6 comprises a graduation part and a set value indication part for indicating the graduation part based on the set value.