A mixed refrigerant including a plurality of component refrigerants circulates in a refrigeration cycle device. An expansion valve includes a power element. A filled fluid filled in the power element is one component refrigerant in the plurality of component refrigerants. A slope of a saturated vapor pressure curve of the filled fluid is larger than the slope of the saturated vapor pressure curve SV0 of the mixed refrigerant. Thereby, an opening degree of the expansion valve can be prevented from exceeding in a low-temperature region, and the opening degree corresponding to a load can be obtained in a high-temperature region.