A valve device for an exhaust gas flow path, the device comprising: a support body; a valve body that is supported by the support body so as to be rotationally movable about a first rotation axis and that opens and closes a communicating flow path that communicates an upstream chamber and a downstream chamber in an exhaust gas flow path with each other; a first link member supported by the support body so as to be rotationally movable about a second rotation axis; a second link member supported by the valve body so as to be rotationally movable about a third rotation axis; and a biasing member to bias the valve body in a valve closed direction, wherein the first link member and the second link member are connected to each other so as to be mutually rotationally movable about a fourth rotation axis, wherein the first rotation axis, the second rotation axis, the third rotation axis, and the fourth rotation axis are parallel to one another in an axial direction, wherein, in a plane orthogonal to the axes, an angle formed by a first link line connecting the second rotation axis and the fourth rotation axis to each other and a second link line connecting the third rotation axis and the fourth rotation axis to each other is formed largest in a state in which the communicating flow path is closed by the valve body, wherein a stopper mechanism to limit the angle formed by the first link line and the second link line is provided, the device being characterized in that the stopper mechanism limits the angle formed by the first link line and the second link line to an angle smaller than 180 degrees, and in that, in the plane orthogonal to the axes, the angle formed by the first link line and the second link line is an angle close to 180 degrees in the state in which the communicating flow path is closed by the valve body. a support body; a valve body that is supported by the support body so as to be rotationally movable about a first rotation axis and that opens and closes a communicating flow path that communicates an upstream chamber and a downstream chamber in an exhaust gas flow path with each other; a first link member supported by the support body so as to be rotationally movable about a second rotation axis; a second link member supported by the valve body so as to be rotationally movable about a third rotation axis; and a biasing member to bias the valve body in a valve closed direction, wherein the first link member and the second link member are connected to each other so as to be mutually rotationally movable about a fourth rotation axis, wherein the first rotation axis, the second rotation axis, the third rotation axis, and the fourth rotation axis are parallel to one another in an axial direction, wherein, in a plane orthogonal to the axes, an angle formed by a first link line connecting the second rotation axis and the fourth rotation axis to each other and a second link line connecting the third rotation axis and the fourth rotation axis to each other is formed largest in a state in which the communicating flow path is closed by the valve body, wherein a stopper mechanism to limit the angle formed by the first link line and the second link line is provided, the device being characterized in that the stopper mechanism limits the angle formed by the first link line and the second link line to an angle smaller than 180 degrees, and in that, in the plane orthogonal to the axes, the angle formed by the first link line and the second link line is an angle close to 180 degrees in the state in which the communicating flow path is closed by the valve body.