To provide a high-COP refrigeration cycle while supercooling a refrigerant flowing in an expansion device of a low temperature-side refrigeration cycle, in the refrigeration cycle device provided with a multiple refrigeration cycle.

A low temperature-side refrigeration cycle Rb is configured to successively connect a low temperature-side compressor 5, a secondary-side flow passage 4b of a cascade heat exchanger 4, a primary-side flow passage 6a of an auxiliary heat exchanger 6, a low temperature-side expansion device 7, and an evaporator 8 using a refrigerant piping P. One end 9a of the low temperature-side refrigeration cycle Rb is connected to the refrigerant piping P between the secondary-side flow passage 4b of the cascade heat exchanger 4 and the auxiliary heat exchanger 6 which is located between the secondary-side flow passage 4b of the cascade heat exchanger 4 and the low temperature-side expansion device 7, and the other end 9b is provided with a bypass circuit 9 connected to a compression chamber of intermediate pressure during a compression stroke of a low temperature-side compressor 5. In addition, the bypass circuit 9 is provided with an auxiliary expansion device 10 and a secondary-side flow passage 6b of the auxiliary heat exchanger 6 in the middle.