Abstract: A valve device includes a valve seat, a valve body, a buffer, and a non-overlapping portion. The valve seat has an opening that communicates with an exhaust flow path. The valve body is configured to open and close at least a part of the opening. The buffer is disposed between the valve seat and the valve body and is more flexible than the valve seat. The non-overlapping portion is configured so that the valve seat and the valve body do not overlap each other in an opening and closing direction of the valve body at at least a part of an outer periphery of the valve body in a state where the valve body is closed.