Abstract: An object of the present invention is to provide a power transmission device in which the cushioning effect due to a cushioning member can be maintained for a long period of time, and the process for assembling the cushioning member can be simplified. In the power transmission device in accordance with the present invention, A plurality of convex portions (30a) are provided on the outer peripheral surface of a cushioning rubber (30) at intervals in the circumferential direction. A plurality of concave portions (10b) are provided in the inner peripheral surface of a pulley (10) at intervals in the circumferential direction. The convex portions (30a) are fitted in the concave portions (10b). Therefore, the cushioning rubber (30) transmits turning force while being deformed elastically in the shear direction between the pulley (10) and an inner ring (20).