A process for preparing a lithographic printing plate, which has excellent printability, durability and stability, which comprisingimagewise irradiating a lithographic printing plate material comprising a support having thereon a light-sensitive layer comprising, as essential components, (a) an inorganic material and (b) at least one member selected from the group consisting of a metal and a metal compound, both of which are in contact with each other and which, upon irradiation with electromagnetic radiation, react with each other forming a mutually diffused state and as a result, a difference in the hydrophilic property or in the oleophilic property occurs between the areas irradiated with the electromagnetic radiation and the non-irradiated areas, with electromagnetic radiation, andthen wetting the light-sensitive layer thereof with wetting solution containing (i) at least one compound selected from the group consisting of thiourea and a thiourea derivative and (ii) as an acid component, at least one compound selected from the group consisting of an inorganic acid, an acidic inorganic salt, and an organic acid.