In a rotary damper capable of being easily assembled by reducing the remaining air inside an accommodation portion and reducing the non-uniformity of damping torque, a center shaft 73 is provided in the center of a fixing and supporting member 71, an inner cylinder wall 63 into which the center shaft 73 is inserted rotatably is provided in a driven rotation member 61, an O ring 81 which prevents the leakage of viscous fluid 101 from between the driven rotation member 61 and the fixing and supporting member 71 is provided, a first path 70 which enables the accommodation portion 91 to communicate with its outside is provided between the center shaft 73 and an inner circumference face of the inner cylinder wall 63, and a hole 63c which allows the bottom side of the O ring 81 inside the accommodation portion 91 to communicate with the first path 70 is provided in the driven rotation member 61.