PURPOSE: To reduce the difference between the actual temperature and set temperature even if there was an error in the sensor installation location by installing temperature sensors across a cooling unit so as to allow the temperature control by computing the refrigerator temperature based on the detected temperatures by said sensors, while, if there is a malfunction in one of the sensors, the detected temperature by the other sensor is used as the refrigerator temperature.

CONSTITUTION: When first and second temperature sensors 9, 10 are operating normally, the temperature of the refrigerator interior space 11 is computed from those which are detected by them, and the control output will be ON if the refrigerator temperature is higher than the upper limit of the set temperature, OFF if that is lower than the lower limit and will be continued if the refrigerator temperature is inbetween. If the sensor 9 is found to be faulty and the sensor 10 is working normally, the temperature detected by the sensor 10 is used as the refrigerator temperature, and afore-said control is performed. If both of them are faulty, the control output will be ON unconditionally. Therefore if either one of the sensors becomes faulty, the control will be such that the control point is displaced by Δt/2 in relation to the set refrigerator temperature. Further, even if the sensor locations are inadvertently reversed, the control will be not much out of the set temperature, increasing the versatility of the on-site sensor installation.