Abstract: Disclosed is a process for treating a plate surface of a lithographic printing plate, which comprises, after exposing and developing a lithographic printing plate having a support and at least a silver halide emulsion layer and a physical development nuclei layer provided on the support, treating the plate surface of the lithographic printing plate with a plate surface-treating solution containing at least one water-insoluble compound having a mercapto group or a thione group and a compound represented by the following formula (1): ##STR1## wherein A represents a vinyl monomer unit having a carboxyl group, B represents a copolymerizable ethylenic unsaturated monomer unit, M represents a cation, k represents 30 to 90 mole %, m represents 10 to 50 mole %, and n represents 0 to 50 mole %.

Abstract: The present invention provides a lithographic printing plate material which comprises a grained and anodized aluminum support and a silver halide emulsion layer between which physical development nuclei are provided wherein said aluminum support have 500 or more pits having a diameter of 0.03-0.30 .mu.m and an average diameter of 0.05-0.20 .mu.m per 100 .mu.m.sup.2.