A control device and for controlling an air conditioner, comprising: a plurality of function keys for inputting a manipulation signal for manipulating operating conditions of the air conditioner and; a first display unit for displaying a changeable first image; and a second display unit for displaying a preset second image, wherein the operating conditions include predetermined setting items, and when one of the setting items is selected by the manipulation of the plurality of the function keys, the first image and second image corresponding to the selected setting item or a set value of the selected setting item are simultaneously displayed on the first display unit and the second display unit characterized in that: the setting items are changed in a predetermined setting mode state, and the plurality of function keys include a first function key for inputting a manipulation signal to enter the setting mode, whenever the first function key is pressed in the setting mode, the setting item capable of manipulating a set value is changed, and the plurality of function keys include second function keys for moving a manipulation target between a selected setting item and a set value of the selected setting item when one of the setting items is selected, third function keys for changing the set value of the setting item within an operable range, and a fourth function key for setting the set value of the selected setting item. a plurality of function keys for inputting a manipulation signal for manipulating operating conditions of the air conditioner and; a first display unit for displaying a changeable first image; and a second display unit for displaying a preset second image, wherein the operating conditions include predetermined setting items, and when one of the setting items is selected by the manipulation of the plurality of the function keys, the first image and second image corresponding to the selected setting item or a set value of the selected setting item are simultaneously displayed on the first display unit and the second display unit characterized in that: the setting items are changed in a predetermined setting mode state, and the plurality of function keys include a first function key for inputting a manipulation signal to enter the setting mode, whenever the first function key is pressed in the setting mode, the setting item capable of manipulating a set value is changed, and the plurality of function keys include second function keys for moving a manipulation target between a selected setting item and a set value of the selected setting item when one of the setting items is selected, third function keys for changing the set value of the setting item within an operable range, and a fourth function key for setting the set value of the selected setting item. the setting items are changed in a predetermined setting mode state, and the plurality of function keys include a first function key for inputting a manipulation signal to enter the setting mode, whenever the first function key is pressed in the setting mode, the setting item capable of manipulating a set value is changed, and the plurality of function keys include second function keys for moving a manipulation target between a selected setting item and a set value of the selected setting item when one of the setting items is selected, third function keys for changing the set value of the setting item within an operable range, and a fourth function key for setting the set value of the selected setting item.