A flywheel assembly 1 includes a flywheel 2, a flexible plate 3 and a dynamic damper 4 to reduce the noise of an engine during acceleration of the speed of the engine. The flexible plate 3 connects the flywheel 2 with a crankshaft 5 so as to be able to oscillate in a bending direction. The dynamic damper 4 includes a mass body 13, and a plate 14 which connects the mass body 13 with the flywheel 2 so as to be able to oscillate in a bending direction.