In a guide vane according to an embodiment of the invention, where in a section perpendicular to a guide vane rotation axis, a curvature of a contour line forming a runner side vane surface of the guide vane is referred to as a positive curvature when the contour line is formed to be convex, while the curvature of the contour line is referred to as a negative curvature when the contour line is formed to be concave, a negative curvature portion where the curvature of the contour line becomes negative is provided on the runner side vane surface. The negative curvature portion is formed from an upper end portion to a lower end portion of the runner side vane surface.