A power transmission system has a Neidhart structure in which a damper is shearing-deformed while being press-deformed when torque is applied to a pulley. The torque is transmitted from the pulley to a center hub by the reaction force in response to a vector component of the deformation of the damper, parallel to the pulley rotation direction, while a torque fluctuation is reduced by the deformation of the damper. Thereby, it is possible to set an elasticity modulus of the damper to be smaller. Therefore, it is possible to provide a compact power transmission system having a reduced torque fluctuation.