Six through holes are formed in pinion gear supporting portions of two input plate members working as a carrier that supports pinion gears of a rotary inertia mass damper. The two input plate members are opposed to each other in such a manner that the through holes are aligned with each other. The through holes support the pinion gear. The input plate members are coupled with each other by means of rivets passing through the through holes located on both sides of the through holes. This configuration ensures strength (rigidity) of the carrier, suppresses deformation of a planetary gear, and improves meshing accuracy of gears.