Abstract: A rotary damper is adapted to exert braking force to an upswung door, a toilet lid or the like when the door is closed and dampen the impact produced by the closing door by a damping force far greater than the one obtained by a conventional rotary damper using viscous shearing resistance. The rotary damper can also make the door open by a force far smaller than a conventional rotary damper. A movable shaft is rotatably housed in a casing and has a cylindrical shaft section including an arcuate non-resilient section extending from a peripheral edge thereof to an axial base line close to the other free peripheral edge thereof and an eccentric resilient section extending from the axial base line to the other free peripheral edge thereof with its eccentricity increasing as a function of the distance from the base line relative to the radius of curvature of the inner peripheral surface so as resiliently abut the inner peripheral surface.