Abstract: A ladder leveling device having a pair of hydraulic cylinder/piston units to be secured at the outside lower ends of the ladder side rails in a manner so that the piston rods of the units extend as ladder supports. The working chambers of the units are in fluid communication with each other through a valved passageway which, when open, allow both piston rods to adapt to an irregular supporting surface while the ladder is oriented in a vertical plane. Upon closure of the passageway to isolate the working chambers of the respective units, the piston rods act as rigid extensions of the ladder side rails. Valving of the passageway is effected by a actuating member extending between the side rails in the region of a lower ladder rung so that the member may be depressed to close the passageway by one ascending the ladder in simply stepping on the actuating member.