To control an operation of a vapor compressing cooling system in the most-suitable efficiency while assuring a stability having a large surplus amount and a relative fast responding characteristic under an operation of an EEV control circuit by a less-expensive proportional control.

A vacant container 1 is arranged between the second passages 11 and 12 connecting an outlet of a gasification device 2 with a compressor 6. Both separation of liquefied refrigerant and over-heating of vapor refrigerant are carried out in the vacant container. With such an arrangement as above, the liquefied refrigerant is prevented from reaching the second temperature sensor 7 for sensing a temperature of the flowed-out vapor, the predetermined over-heating is accomplished at a downstream side of the gasification device 2 so as to stabilize the over-heated condition.