In order to provide a refrigeration cycle device that is compact and efficiently utilizing an expansion machine and reduced in manufacturing cost through the use of a first compressor and second compressor driven by an expansion machine, a heat radiator and an on-off valve are disposed between the first and the second compressors and the second heat radiator is utilized irrespective of the operating mode such as the cooling or heating operation. Also, the heat transfer area ratio, which is a ratio of the heat transfer area of the second heat source side heat exchanger relative to the total heat transfer area of the heat transfer areas of said first and second heat source side heat exchangers, is set, according to the air speed distribution, within a range at which the COP is at its peak. Thus, the second heat source side heat exchanger can be utilized even during the heating operation, providing a high efficiency refrigeration cycle device.