Method of making a lithographic printing plate

In a process for preparing a lithographic printing plate which comprises (1) preparing a light-sensitive lithographic printing plate precursor comprising a metal support having thereon, in succession, a light-sensitive composition layer and a transparent film, said light-sensitive composition layer having a stronger adhesion to one of said support and said film than the other one in its unexposed state and having a stronger adhesion to said the other one than said one in its exposed state, by coating said light-sensitive composition layer on said support and then placing said transparent film over said light-sensitive composition layer and thereafter (2) imagewise exposing said precursor and (3) peeling said imagewise exposed precursor apart to remove, together with said film, areas which have a stronger adhesion to said film in said imagewise exposed light-sensitive composition layer by utilizing the difference in adhesion to said support and to said film between the exposed areas and the unexposed areas of said light-sensitive composition layer, whereby to obtain the lithographic printing plate, the improvement which comprises prior to said coating, subjecting the surface of said support to be adjacent said light-sensitive composition layer to an anodic oxidation treatment and then treating said surface successively with (1) an aqueous solution containing phosphoric acid, and (2) an aqueous solution containing at least one water soluble silicic acid or salt thereof selected from the group consisting of a silicic acid or silicic acid salt and then coating the treated surface with said light-sensitive composition layer.