PURPOSE: To suppress a rise of temperature in a freezing chamber and to keep the quality of stored articles by detecting quickly an abnormal state of a cooling operation executed by a switchover after completion of defrosting, when this state occurs.

CONSTITUTION: When completion of defrosting is detected by a defrosting completion thermostat 27, it is detected from a temperature signal from an in-freezer temperature thermostat 28 whether a cooling operation is executed normally or not. When the cooling operation is not executed normally, it is possible to stop the operation of equipment or to inform a user of the abnormality by an alarm.