A negative planographic printing plate precursor includes a negative recording layer on a support. The support has a hydrophilic surface with hydrophilic graft polymer chains present therein. The negative recording layer contains a radical generator, a radical-polymerizing compound, and a photo-thermal converting agent. Preferably, the hydrophilic graft polymer chains are directly bonded to the support surface or to an intermediate layer formed on the support surface, or are introduced into a crosslinked polymer film structure.