PURPOSE: To obtain clear-cut images in a short time by a method in whch a diazo photo-sensitive layer is contacted with one face of a wetting-resistant plate on which wettable images are formed, a basis liquid is impregnated into the other face, and images are developed in the part of photo-sensitive layer.

CONSTITUTION: A negative plate 1 is obtained by forming wettable images on a wetting-resistance base plate, e.g., stencil negative plate, etc., by writing by pencil, heating by heat-sensitive head, etc. Then, the negative plate 1 is placed on a diazo photo-sensitive paper 2, a push plate 4 is clamped by stop screw 5 to fix the photo-sensitive paper 2, and a roller 6 of a continuously cellular resin, felt, etc., impregnated with a basic liquid (e.g., an aqueous solution of an alkali or alkaline earth metal hydroxide) is moved while pressing it on the negative plate 1 in such a way that the base liquid can reach the photo-sensitive paper 2 through the wettable part of the plate 1 and thereby the image of diazo dyes by coupling reactions can be formed. Then, the paper 2 is removed from the plate 3 and non-image part is decomposed and whitened by sunshine or room illumination.