A valve device for a silence opens a bypass passage provided in the silencer to flow exhaust gas through the bypass passage when exhaust gas pressure rises to a certain pressure. The valve device includes a base having a valve opening through which exhaust gas flows, and a plate-like valve for opening and closing the valve opening. The plate-like valve is fixed to the base at its proximal portion, and is bent at both edges thereof in a certain range extending from its distal end toward the proximal portion.