PURPOSE: To control a temperature within a show case so as to attain a temperature rage which is approximate to a predetermined temperature by a method wherein the newest turning-on or turning-off time interval of a solenoid valve for refrigerant liquid under a normal operation is stored and then the solenoid valve for the refrigerant liquid is opened or closed in response to the stored turning-on or turning-off time interval when a temperature sensing sensor shows an abnormal condition.

CONSTITUTION: An ON time and an OFF time of a refrigerant liquid solenoid valve are calculated by a temperature adjusting output time calculation part 16, they are inputted to a memory part 17 through a CPU 11 so as to store the newest ON time temperature and OFF time. In the case that a sensor abnormal state judging part 18 judges that an abnormal state occurs in either a show case temperature sensor 12 or a blowing temperature sensor 13, the CPU 11 turns off the abnormal state sensor and outputs ON/OFF signals in response to data of only the normal temperature detecting sensor. In addition, in the case that abnormal state occurs in both sensors, the CPU 11 performs a duty cycle control in response to the ON/OFF time stored in the memory part 17 and then outputs the ON/OFF signal for the refrigerant solenoid valve corresponding to the ON/OFF time.