A double rotation type scroll expander that expands steam includes a first drive scroll, a second drive scroll, a driven scroll, a rotation mechanism that supports the driven scroll rotatably, and a revolving mechanism that couples the driven scroll to the first drive scroll and the second drive scroll to be capable of revolving relative thereto. The revolving mechanism includes: a plurality of metal revolving pins provided respectively between a first drive end plate of the first drive scroll and a first driven arm of the rotation mechanism and between a second drive end plate of the second drive scroll and a second driven arm of the rotation mechanism; and a plurality of metal revolving discs provided in relation to the respective revolving pins and disposed such that respectively corresponding revolving pins are coupled thereto eccentrically.