A method of making a printing plate from a heat-sensitive PS plate of a positive-working mode for lithographic printing includes the steps of exposing the heat-sensitive PS plate to light and developing the PS plate using an alkaline developing solution containing at least one compound selected from the group consisting of cationic surfactants and compounds having three or more of an ethylene oxide-terminal group in the molecule thereof. The PS plate has a substrate and an image forming layer formed thereon, said image forming layer comprising a lower layer which is formed on the substrate and contains a water-insoluble and alkali-soluble resin and an upper heat-sensitive layer which is overlaid on the lower layer and contains a water-insoluble and alkali-soluble resin and an infrared absorption dye and exhibits an elevated solubility with respect to alkaline aqueous solutions when heated.