A method of manufacturing a light sensitive planographic printing plate which has an image forming layer containing (A) a coloring material having an absorption in a wavelength range of 700 nm through 1200 nm and (B) a radical generator on a support and is exposed by a laser beam with a light emission wavelength in a wavelength range of 700 nm through 1200 nm, the method comprising: at least coating process, dry process, cutting process, and inspection/sorting process, wherein either of the coating process, the dry process, the cutting process, or the inspection/sorting process is carried out under light of a light source comprising a light-emitting diode with an emission wavelength maximum in a range of 400 nm through 500 nm and a fluorescent phosphor to emit an yellow light by absorbing a light emission of the light-emitting diode.