Abstract: The ladder leveling adapter comprises a pair of spacers adapted to be secured outwardly on the side rails of the ladder between two interconnecting rounds. An elongated bar having a median slot parallel to the rail extends over the spacers and projects below the rails. Each rail and each adjacent elongated bar are connected together by a pair of threaded rods having a nut threadedly mounted on the inner side of the rail and quick release tightening means on the outer side of the bar. A friction means is mounted around each rod between the spacer and the bar for preventing a longitudinal slipping between the bar and the rail. The quick release tightening means comprises a knob axially mounted on the rod having a flat surface abuting on the bar and a lever for slidingly moving the knob against the bar. The knob includes a pin which extends in the slot of the bar for preventing the rotation of the lever relative to the slot, the pin having a length greater than the releasing distance of the release means.