A refrigerator has a coolant cooler for cooling a coolant at the entrance of a flow control valve, when the cooling amount in the coolant cooler is deficient as well as excessive. The refrigerator includes a compressor for compressing the coolant, a radiator for radiating heat from the coolant, a coolant cooler for cooling the coolant, a flow control valve for regulating the flow volume of the coolant, an evaporator for evaporating the coolant, and a heat-exchange-amount control for controlling the amount of heat exchanged in the coolant cooler. The coolant is circulated through the compressor, the radiator, the coolant cooler, the flow control valve, and the evaporator, in that sequence.