A refrigerant cycle device is provided to reduce noise and to improve reliability of the refrigerant cycle device by using carbon dioxide as a refrigerant. A refrigerant cycle device comprises a heat exchanger(20). The heat exchanger is prepared in the form of a dual pipe including a first refrigerant pipe(21) and a second refrigerant pipe(22). The first refrigerant pipe is formed therein with a first fluid path(30). High-pressure refrigerant having passed through a gas cooler flows in the first fluid path. A second fluid path(40) is formed between the first and second refrigerant pipes. Low-pressure refrigerant having passed through an evaporator flows in the second fluid path. Refrigerants flowing through the first and second fluid paths are heat-transferred to each other. The heat exchanger has a spiral structure to enlarge a heat-exchange area.
