To realize a printing plate body with a smooth surface free from the abnormalities of a surface shape such as creases, mottles, ripples and strains, when the printing plate body is manufactured on a printing press.

A photosensitive plate agent is supplied and applied to the surface of a printing plate body fixed on the plate cylinder of the printing press and thereby, a photosensitive plate agent layer is formed. Next, the photosensitive plate agent layer is dried, then a printing element part is formed and the photosensitive plate agent layer other than the printing element part is removed. When the printing plate body is manufactured on the printing press, the drying process comprises a preliminary drying step including the rotation of the plate cylinder in a windless condition.