PURPOSE: To contribute to the power saving at the bedtime by equipping a means to detect a state of light and darkness in the room, a means to measure the continuous period of time of a darkness, and a means to set a sleeping time automatically when the continuous period of time of a darkness reaches a specified value.

CONSTITUTION: Whether the inside of a room is under a darkness or not is judged based on a detecting signal from a light sensor 4. When the inside of a room is under a darkness, a timer 6a is set for a specified period of time Ta, and the measurement of a continuous period of time (Ta) of the darkness is started. When the continuous period of time (ta) of the darkness reaches the specified value Ta, it is judged that a person in the room has gone to bed, and a monitor display lamp 5 is lit up, and it is displayed that the air-conditioner is under a sleeping timer operation, and a set temperature value by manual control is automatically adjusted, and a sleeping timer 6b is automatically set for a specified period of time Tb. Then, the measure of a continuous period of time (tb) of a dark condition is started, and when the continuous period of time (tb) reaches the specified value Tb, the main power source of an air conditioner 1 is automatically turned off, and the operation of the air-conditioner 1 is stopped.