A silencer comprises a casing, an inlet pipe for introducing an exhaust into the casing, and an outlet pipe for discharging the exhaust out of the casing. A lid is provided at an exhaust inflow side opening of the outlet pipe and arranged to close the exhaust inflow side opening. The lid has an exhaust inlet for flowing the exhaust into the outlet pipe, a valve body for opening and closing the exhaust inlet, and at least one communication hole formed separately from the exhaust inlet. The valve body is configured to be rotationally movable about a rotation axis of the valve body inside the outlet pipe. The at least one communication hole is provided closer to the rotation axis of the valve body than the exhaust inlet.