A shock absorber includes a casing that is filled-in with a working fluid, a cylinder body that is housed in the casing and that forms chambers inside and outside the cylinder body, a sliding shaft that passes through the cylinder body and forms a flow path between the sliding shaft and the cylinder body and engages a movable contact, and a piston that is fixed to the sliding shaft and that is housed inside the cylinder body. An outer diameter of the piston is larger than a diameter of the sliding shaft. The piston can be slid in an inner peripheral surface of the cylinder body while ensuring waterproofing and causes the working fluid to move inside and outside the cylinder body and receives, due to a flow resistance at the time of the working fluid passing through the flow path, a braking force.