A damper includes a piston provided with a rod, and a cylinder storing the piston, and generates a braking force by a movement or relative movement of the piston. The cylinder is provided with width-side wall portions and thickness-side wall portions, and a shape in a cross section of the cylinder in a direction orthogonal to a moving direction of the piston is flat. The cylinder has a connection portion on an open side thereof, and the connection portion bridges the width-side wall portions.