The present invention discloses a negative planographic printing plate precursor for infrared exposure having an image recording layer containing an infrared absorbing agent, a radical generator and a radical polymerizable compound on a support characterized in that a sensitivity ratio (S¹/S⁶⁰) of a sensitivity (S⁶⁰) when developed 60 minutes after infrared laser exposure to a sensitivity (S¹) when developed one minute after exposure is at least 0.5 and less than 1.0 in the image recording layer. It is preferable that this composition contains a polymer compound which has a functional group having high radical reactivity and can be dissolved or swollen in water or an aqueous alkali solution.