PURPOSE: To eliminate adverse effect due to dust or the like present between a developed film and a hard transparent plate, by overlaying the developed film, a light transmitting soft synthetic resin layer, and a hard transparent plate in succession on a photosensitive printing plate, bringing them into intimate contact with one another, and then, exposing them from the hard transparent plate.

CONSTITUTION: The light transmitting soft synthetic resin layer 17 is overlaid on the pressing face 16 of the hard transparent plate 14. The photosensitive printing plate 12 is placed on a base plate 10, on this photosensitive face 12a of the plate 12 the developed film 13 is overlaid, the plate 14 is overlaid so as to bring the layer 17 into contact with the film 13, and pressure is applied to the plates 10 and 14 to hold the plate 12, the film 13, and the layer 17. The face 12a is exposed from the plate 14 to project the image of the film 13 surface to the plate 12. At that time, even if foreign matters 18 are present between the film 13 and the layer 17, they intrude into the layer 17 to maintain an intimate contact state. The matters 18 do not damage the film 13. The matters as small as 15W50μm are little projected on the face 12a with light transmitted around the matters 18.