Autotensioner

An autotensioner comprising a support shaft, a pulley support eccentrically supported by said support shaft, a pulley rotatably supported by said pulley support, a tension imparting means for urging said pulley support in a direction in which said pulley stretches a belt, said pulley support having a cylindrical portion which is concentrical with said support shaft, and damper means disposed between said cylindrical portion and said support shaft for imparting a rocking resistance to said pulley support, characterized in that said pulley support comprises an eccentric ring and a rocking shaft, said eccentric ring has the inner periphery thereof eccentric with respect to the outer periphery thereof, and said rocking shaft is provided at one end thereof with said cylindrical portion and is integrally provided at the other end thereof with a cylindrical small-diameter portion which is inserted in said eccentric ring so as not to rotate relative to said eccentric ring.