A rotary damper for generating a damping force in reaction to an external force by limiting a movement of a viscous fluid, the damper comprising: a fluid holding chamber including an opening section and holding the viscous fluid; a resistance generating member (31, 931) inserted in the opening section of the fluid holding chamber and movable relative to the fluid holding chamber in reaction to the external force; volume changing means (25, 32) partitioning an inside of the fluid holding chamber and configured to compress one of areas within the fluid holding chamber partitioned and to expand another of the areas, with a movement of the resistance generating member (31, 931) relative to the fluid holding chamber; a flow passage connecting between the areas within the fluid holding chamber partitioned by the volume changing means (25, 32); a bushing (4a, 4b) attached to the opening section of the fluid holding chamber and holding slidable the resistance generating member (31, 931) inserted in the opening section of the fluid holding chamber; and an elastic member (8a, 8b) in an substantial annular shape, located between the resistance generating member (31, 931) held by the bushing (4a, 4b) and the opening section of the fluid holding chamber, characterized in that the elastic member (8a, 8b) comprises: an inner peripheral annular part having a rectangular cross section and having an inner peripheral surface pressed against the resistance generating member (31, 931); and an outer peripheral annular part having a rectangular cross section and having an outer peripheral surface pressed against the fluid holding chamber, being larger than the inner peripheral surface in width in the direction of the center axis of the fluid holding chamber; and a coupling part connecting the inner peripheral annular part and the outer peripheral annular part, the coupling part having a width smaller than a width of the inner peripheral annular part and than a width of the outer peripheral annular part in the direction of the center axis of the fluid holding chamber. a fluid holding chamber including an opening section and holding the viscous fluid; a resistance generating member (31, 931) inserted in the opening section of the fluid holding chamber and movable relative to the fluid holding chamber in reaction to the external force; volume changing means (25, 32) partitioning an inside of the fluid holding chamber and configured to compress one of areas within the fluid holding chamber partitioned and to expand another of the areas, with a movement of the resistance generating member (31, 931) relative to the fluid holding chamber; a flow passage connecting between the areas within the fluid holding chamber partitioned by the volume changing means (25, 32); a bushing (4a, 4b) attached to the opening section of the fluid holding chamber and holding slidable the resistance generating member (31, 931) inserted in the opening section of the fluid holding chamber; and an elastic member (8a, 8b) in an substantial annular shape, located between the resistance generating member (31, 931) held by the bushing (4a, 4b) and the opening section of the fluid holding chamber, characterized in that the elastic member (8a, 8b) comprises: an inner peripheral annular part having a rectangular cross section and having an inner peripheral surface pressed against the resistance generating member (31, 931); and an outer peripheral annular part having a rectangular cross section and having an outer peripheral surface pressed against the fluid holding chamber, being larger than the inner peripheral surface in width in the direction of the center axis of the fluid holding chamber; and a coupling part connecting the inner peripheral annular part and the outer peripheral annular part, the coupling part having a width smaller than a width of the inner peripheral annular part and than a width of the outer peripheral annular part in the direction of the center axis of the fluid holding chamber. an inner peripheral annular part having a rectangular cross section and having an inner peripheral surface pressed against the resistance generating member (31, 931); and an outer peripheral annular part having a rectangular cross section and having an outer peripheral surface pressed against the fluid holding chamber, being larger than the inner peripheral surface in width in the direction of the center axis of the fluid holding chamber; and a coupling part connecting the inner peripheral annular part and the outer peripheral annular part, the coupling part having a width smaller than a width of the inner peripheral annular part and than a width of the outer peripheral annular part in the direction of the center axis of the fluid holding chamber.