An expansion valve includes a vibration-proof spring that develops the sliding resistance by biasing a shaft. The vibration-proof spring includes a base portion constituted by a circular plate having a hole, through which the actuating rod can be inserted, in the central region, a plurality of spring portions, which is installed upright on the base portion and which is so formed as to come in contact with the periphery of the actuating rod, and a plurality of supporting pieces, which extend outward from the base portion and which is formed so that the supporting pieces can be stopped by the body. The supporting piece is structured such that the supporting piece includes a low-rigidity portion whose rigidity is lower than that of the base portion.
