Abstract: A clamping device is provided for the adjustable attachment of stabilizer legs to a ladder in a manner to prevent lateral movement of the ladder. The clamping device has paired elongated jaws interconnected by a hinge and spring and adapted to slideably engage the legs of the ladder. A spreader rod is pivotably associated with the hinge and has a free end adapted to move in a vertical path. A stabilizer leg is attached to the free end of the spreader rod. When the spreader rod is swung downwardly, it forces the jaws into gripping contact with the leg of the ladder. When the spreader rod is swung upwardly, the jaws open sufficiently to permit sliding movement along the leg of the ladder.