PURPOSE: To improve cooling capacity by a method wherein dryness at the outlet part of a refrigerant vaporizer is controlled to an optimum value.

CONSTITUTION: The opening time of a first flow rate regulating valve 4 is controlled so that dryness of a refrigerant detected by a dryness sensor 14 located in the vicinity of the outlet part of a refrigerant vaporizer 6 is adjusted to, for example, 0.8-0,9. Through regulation of an amount of a refrigerant in an accumulator 7 sucked from the suction part of an ejector 5, an amount of a liquid refrigerant flowing in the refrigerant vaporizer 6 is increased. This constitution enables suppression of lowering of transmissibility on the refrigerant side at the outlet part of the refrigerant vaporizer 6 during operation of a freezing cycle 1.