PURPOSE: To reduce a loss in the continuous operation of a cooler due to the saturation of room temperature by a method wherein the insensitive zone of the room temperature during the operation of the cooler is automatically corrected according to the room temperature lowering condition.

CONSTITUTION: In the case of the titled method, if the correction of the OFF point of the cooler is taken as a primary function of the operating time of the cooler, the OFF point is corrected by one step in response to a pulse signal generating every predetermined time interval. For example, according to the attached graphs, the length of no correction time is 15min and a correcting point is made higher by 0.1°C every three minutes after the lapse of no correction time of 15min. Accordingly, in the case of the temperature drop line (l2), the cooler is stopped after a lapse of 30min when no correction is made but after the correction of the OFF point, it is stopped after a lapse of 24min. Likewsie, in the case of the temperature drop line (l3), the cooler is stopped after a lapse of 45min when no correction is made but after the correction of the OFF point, it is stopped after a lapse of 31W32min. Further, in the case of the temperature lowering line (l6), the cooler is stopped after a lapse of 90min when no correction is made but after correction, it is stopped after a lapse of 45min from the time of correction. The above-mentioned OFF point correction is made after the room temperature enters the insensitive zone but is not made during the time when the room is cooled from the point (a) down to the set temperature point (b) and the correction is made when the room temperature lowers down below the point (b).