A set back timer for an air conditioner is provided with a display screen (15) for the representation of information about normal and set back operations of the air conditioner, wherein a normal operation time period display (53) indicating a time period of the day during which period a normal operation is carried out and a set back time period display (64) indicating a time period in the normal operation time period during which period a set back operation is carried out are displayed independently of each other on the display screen (15). Such arrangement enables an air conditioner user to easily and correctly confirm, at a glance, the relationship between a normal operation time period and a set back operation time period in the normal operation time period for the day, and the contents of a setting can be confirmed remarkably easily, thereby contributing to improvements in air conditioner operability.