Disclosed is a process of preparing a planographic printing plate from a light sensitive planographic printing plate material comprising a hydrophilic support and provided thereon, an image formation layer containing (A) a polymerization initiator selected from a hexaarylbisimidazole compound and a diazo resin, and (B) an alkali soluble resin with an acid value of 5 to 200 having an acryloyl group or a methacryloyl group, the alkali soluble resin being obtained by reacting a vinyl copolymer having a monomer unit derived from acrylic acid or methacrylic acid with an epoxy compound having an acryloyl group or a methacryloyl group in the molecule, and, the process comprising the steps of imagewise exposing the light sensitive planographic printing plate material to ultraviolet laser, and removing an image formation layer at non-exposed portions with an aqueous alkali solution to form an image.