PURPOSE: To enable to perform energy saving cooling operation, by so constituting that a signal increasing a given temperature by an arbitrary value becomes applicable when illuminance detected by a photodetector becomes lower than the arbitrarily set level.

CONSTITUTION: A signal is applied to a control part 4 when illuminance of sunlight sensed by a photodetector 1 becomes lower than the arbitrary illuminance and upon receipt of the signal by the control part 4 a signal raising a given temperature by an arbitrary value ΔT°C is applied to a room temperature adjuster 3 by the control part 4, in the title operation controller consisting of a room temperature detector 2, the room temperature adjuster 3, the control part 4 and a relay output part 5 for a compressor. A signal is applied to a relay output part 5 from the control part 4 due to a relation between the room temperature detected by the detector 2 and the given temperature which has been raised by ΔT°C. With this construction, an operation factor of the compressor is reduced and far more energy saving cooling operation can be performed.