PURPOSE: To efficiently obtain a good-quality flexographic plate having a pattern faithful to a negative film through one step of development processing by protecting the exposed part of a photosensitive resin layer and its outline border with a resin film soluble in a developing solution and developing it.

CONSTITUTION: The photosensitive resin layer formed on a substrate is selectively exposed to actinic rays through the negative film closely attached to the layer. The resin film cut by 2-10mm larger than the border of the pattern of the exposed part is applied to the corresponding to the pattern as a masking member, and the pattern is developed with the developing solution. Accordingly, the masked part is developed after the masking member has been dissolved off and the developing time is substantially shorter than that of the nonmasked part.