In an exhaust system for an internal combustion engine, an output member is configured to transmit power generated by a motor to a valving element via a valve stem. An output shaft is disposed on a rotation central axis of an output gear and coupled with the output gear to be rotatable integrally therewith. A follower is disposed eccentrically relative to a rotation central axis of the output shaft and connected to the output shaft to be rotatable integrally therewith. A first accommodating chamber accommodates at least the valve stem and the follower. A second accommodating chamber accommodates at least the motor and the output gear. A housing includes a housing wall that divides the first chamber from the second chamber. The housing wall includes a first bearing slidably supporting the output shaft in its rotation direction, and a cylindrical first bearing holder holding outer periphery of the first bearing.