PURPOSE: To perform proper cooling control and enhance the cooling effect of a refrigerator by detecting temperature change of cooling water before said cooling water flows into a cooling pipe of a condenser, entering this electric signal into an arithmetic unit, and controlling the opening of a cooling water inlet valve in combination with a pressure signal.

CONSTITUTION: When the temperature of cooling water rises, the cooling water whose temperature is increased, flows into a cooling pipe of a condenser 1, thereby reducing the cooling capacity of the condenser 1. Before the pressure in the condenser 1 is about to rise, an attempt is made to detect a rise in cooling temperature in a cooling pipe 7 with a temperature detector 8. This temperature signal is input into a device 9 which opens a cooling water inlet valve 6 in proportion to the increase in the temperature of the cooling water. As a result, the cooling water inlet valve 6 is opened before the pressure in the condenser 1 rises. Furthermore, the cooling water inlet valve responds to the rise in pressure induced by an increase in the amount of flowing-in refrigerant 3 as in the past so that the opening of the cooling water inlet valve 6 may be controlled, which makes it possible to prevent the generation of phenomenon that the refrigerant 3 reduces its cooling capacity due to the time lag of cooling water capacity control.