To provide a liquid developer and a developing method by which sludge accumulating in a developing tank in long-term processing is decreased and deposition of dirt on a photosensitive lithographic printing plate is decreased.

After a photosensitive lithographic printing plate including a photosensitive layer made of a photopolymerizable photosensitive resin composition comprising a monomer containing an ethylenic unsaturated bond, a photopolymerization initiator and a polymer binder formed on the surface of an aluminum plate supporting body is exposed to an image, the plate is developed with an alkali aqueous solution having pH 8.5 to 12.5 and containing at least an inorganic alkali agent, a polymer having a carboxyl group and an anionic surfactant having an amide group.