To improve the reliability of the Rankine cycle device using a sealed-type expansion machine, the Rankine cycle device 100 according to the present disclosure comprises a pump 1, a heater 2, an expansion machine 3, a radiator 5, and a cooling path 8. The expansion machine 3 comprises an expansion mechanism 11 for extracting a power from the working fluid, an electric power generator 12, a sealed container 10 containing the expansion mechanism 11 and the electric power generator 12, a first inlet 34a, a first outlet 35a, a second inlet 30a, and a second outlet 31a. The radiator 5 is connected to the pump 1 with a flow path to cool the working fluid drained from the second outlet 31a. The cooling path 8 which connects the first outlet 35a to the second outlet 30a has a cooler 4 to cool the working fluid drained from the first outlet 35a.