A method for forming an image on a planographic printing plate precursor including a substrate and an image recording layer disposed thereon, the layer including a hydrophobic precursor and a light-to-heat converting agent. The method includes an image exposing process of exposing the planographic printing plate precursor to infrared radiation to form an image on the image recording layer of the planographic printing plate precursor, and a post-heating process of heating the planographic printing plate precursor to a predetermined heating temperature.