A rotary damper comprising: a shaft including a hollow portion and capable of rotating about a central axis; a pair of side panels that support the shaft rotatably; a case provided between the pair of side panels such that an operating chamber is defined in an interior thereof; a vane provided on the shaft such that a tip end thereof slides against an inner periphery of the case, thereby dividing the operating chamber into a first chamber and a second chamber; a damping valve provided in the shaft to apply resistance to a flow of a fluid traveling between the first chamber and the second chamber; and a compensation mechanism (32, G, L) that is configured to compensate for volume variation caused by variation in a temperature of the fluid, wherein the damping valve includes: a partition wall member inserted into the hollow portion to define, within the hollow portion, a first side valve chamber that communicates with the first chamber and a second side valve chamber that communicates with the second chamber; a first side port and a second side port provided in the partition wall member to connect the first side valve chamber and the second side valve chamber; a first side valve body capable of opening and closing the first side port; and a second side valve body capable of opening and closing the second side port, wherein the compensation mechanism (32, G, L) includes, a sliding partition wall that is inserted into the hollow portion to be free to slide and defines a gas chamber; and a liquid chamber within the hollow portion, and the liquid chamber communicates with one of the first side valve chamber and the second side valve chamber, wherein the first side valve body and the second side valve body are annular leaf valves (34, 35) that are attached to an outer periphery of a rod penetrating the partition wall member so as to be fixed to the partition wall member, wherein the rotary damper further comprises, a partition member provided on a base end of the rod and inserted into the hollow portion so as to partition the liquid chamber from the first side valve chamber; a holder member that holds the rod and closes the second side valve chamber; an outer peripheral screw nut that is screwed to an inner periphery of the hollow portion so as to fix the holder member to the hollow portion; and a step portion provided on the inner periphery of the hollow portion, and wherein the holder member includes, an annular portion attached to the outer periphery of the rod, and a fitting portion provided on an outer periphery of the annular portion and fitted to the hollow portion, and the outer peripheral screw nut sandwiches the fitting portion of the holder member together with the step portion such that the fitting portion is fixed to the hollow portion, characterized in that the rod is formed in a tubular shape so that the fluid can be injected into the liquid chamber from outside the holder member. a shaft including a hollow portion and capable of rotating about a central axis; a pair of side panels that support the shaft rotatably; a case provided between the pair of side panels such that an operating chamber is defined in an interior thereof; a vane provided on the shaft such that a tip end thereof slides against an inner periphery of the case, thereby dividing the operating chamber into a first chamber and a second chamber; a damping valve provided in the shaft to apply resistance to a flow of a fluid traveling between the first chamber and the second chamber; and a compensation mechanism (32, G, L) that is configured to compensate for volume variation caused by variation in a temperature of the fluid, wherein a partition wall member inserted into the hollow portion to define, within the hollow portion, a first side valve chamber that communicates with the first chamber and a second side valve chamber that communicates with the second chamber; a first side port and a second side port provided in the partition wall member to connect the first side valve chamber and the second side valve chamber; a first side valve body capable of opening and closing the first side port; and a second side valve body capable of opening and closing the second side port, a sliding partition wall that is inserted into the hollow portion to be free to slide and defines a gas chamber; and a liquid chamber within the hollow portion, and the liquid chamber communicates with one of the first side valve chamber and the second side valve chamber, a partition member provided on a base end of the rod and inserted into the hollow portion so as to partition the liquid chamber from the first side valve chamber; a holder member that holds the rod and closes the second side valve chamber; an outer peripheral screw nut that is screwed to an inner periphery of the hollow portion so as to fix the holder member to the hollow portion; and a step portion provided on the inner periphery of the hollow portion, and an annular portion attached to the outer periphery of the rod, and a fitting portion provided on an outer periphery of the annular portion and fitted to the hollow portion, and the outer peripheral screw nut sandwiches the fitting portion of the holder member together with the step portion such that the fitting portion is fixed to the hollow portion,