PURPOSE: To reduce the uncomfortable feeling of inhabitants in the objective space of air conditioning, which is caused due to sunshine, with a simple constitution by a method wherein the set value of room temperature in feedback loop series is added or subtracted in accordance with the output signal of a comparator.

CONSTITUTION: When the output voltage signal (a) of a light volume detecting unit 101 is smaller than the output voltage signal (b) of a light volume setting unit 1, the output signal (c) of a comparator 2 becomes H while the same signal becomes L in a reverse case. When the output signal (c) is H, the output voltage signal of a room temperature setting unit 102 is added with a given voltage width by an adding and subtracting device 3 in synchronizing with the generating pulse of output signal (e) of an astable multivibrator 4. When the output signal (c) is L, the same value is subtracted in the same manner. As a result, the room temperature control unit 103 controls a cold and hot water value 104 by the added or subtracted set voltage signal (d). According to this method, the set value in the room temperature control series is changed in every predetermined time based on the output signal of a light volume control series to control the amount of heat supplied excessively.