This invention describes a heat sensitive composition comprising: (A-I) a compound which is represented by the following general formula (I) and generates a radical when heated, and (B-I) a compound having physical and chemical properties that are changed irreversibly by a radical, R—SO2−M+  General formula (I) wherein R represents an alkyl group or aryl group, and M+ represents a counter cation selected from sulfonium, iodonium, diazonium, ammonium and azinium; and a negative planographic printing plate precursor which can be recorded by heat mode using this composition. This invention also describes a planographic printing plate precursor comprising a substrate having disposed thereon a photosensitive layer containing (C-II) a light-heat converting agent, (B-II) a compound having a polymerizable unsaturated group, and (A-II) an onium salt having at least two cation parts in one molecule.