To obtain a stable refrigerating capacity not being affected by fluctuation of outdoor air temperature, without using an intermediate unit.

A sprinkler 17 sprinkling water on a heat exchanger 14 is fitted to a compressor unit 11. A nozzle 19 sprinkles water in a water tank 21 over radiating fins 23 of the heat exchanger 14 to cool them. Thereby the efficiency of heat exchange of the heat exchanger 14 in summer in a warm district is enhanced and a refrigerating capacity equal to the one of a usual extremely low temperature refrigerator equipped with an intermediate unit is obtained. In the case when an ambient temperature T is a prescribed temperature T1 or below, a control part 26 operates a fan 15 at a medium speed and closes a motor-operated valve 29 to stop sprinkling of water. When the temperature is higher than the prescribed temperature T1, it operates the fan 15 at a high speed to increase the quantity of sprinkled water in proportion to ambient temperature T.