A power generation device includes: a one-way clutch which is provided between an output shaft of a speed increaser and a drive shaft of a power generator, and which restricts relative rotation of the output shaft and the drive shaft in one direction and permits relative rotation thereof in another direction; and a plurality of elastic coupling members which are provided between the output shaft and the drive shaft, which are spaced in an axial direction, and which absorb misalignment between the output shaft and the drive shaft. The one-way clutch is disposed in a position axially outside an area between the plurality of elastic coupling members.