To perform subsequent cold storage operation effectively in an appropriate time when cold is stored following to the delivery of very short time or when cold storage operation is interrupted temporarily.

The low temperature compartment incorporates a cold storage agent, a refrigerating system for storing cold by cooling and freezing the cold storage agent, and a sensor for detecting the temperature of the cold storage agent. At the time of cold storage operation through the refrigerating system, the refrigerating system is operated for a set time after the temperature detected by the temperature sensor of the cold storage agent dropped down to a specified level so that the cold storage agent is frozen completely. In such a low temperature compartment, the set time is regulated depending on the time elapsed after ending the operation of the refrigerating system and the regulation rate is varied depending on the outdoor air temperature.