PROBLEM TO BE SOLVED: To maintain freshness of a food by a method wherein the number of revolutions of a refrigerator fan is reduced to a minimum and the increase of a refrigerator temperature is suppressed to a minimum, in operation right after defrosting of a refrigerator on which an inverter is mounted. SOLUTION: By detecting a defrosting completion signal from a defrosting completion detecting means 10, an output is fed to a number of revolutions of fan correcting means 12. The minimum number of revolutions is selected in getting priority over the number of revolutions decided by a temperature difference between a refrigerator temperature and a set temperature. Cooling air has the efficiency of heat-exchange being improved in such a away that the number of revolutions of a refrigerator fan 8 is suppressed by being delayed by a time in which operation of a timer 13 is completed or temperature by a vaporiser temperature detecting means attains a given value and an airflow is reduced, and the cooling air is fed. Thereafter, the number of revolutions is increased to a value decided by a temperature difference between the refrigerator temperature and the set temperature and a cooling airflow is increased.