A scroll-type expansion machine includes an expansion mechanism including an orbiting scroll and a first fixed scroll for expanding a refrigerant and recovering a power, a sub-expansion mechanism including an orbiting scroll and a second fixed scroll for compressing the refrigerant by the power recovered by the expansion mechanism, and a seal ring disposed in at least one of an outer circumference portion of the sub-compression mechanism or an outer circumference portion of the expansion mechanism. An oil flow path is opened in an upper space of a hermetic vessel to make the upper space and a lower space at a compressed pressure of the sub-compression mechanism, and the lower space is provided with an oil pipe for communicating with the main compressor.