PURPOSE: To obtain a photosensitive resin compsn. superior in image reproducibility, printing aptitude, water developability, etc. by mixing a photopolymerizable monomer having an ethylenically unsatd. bond, and a specified polymer with a perfectly or partially saponified polyvinyl acetate.

CONSTITUTION: A photosensitive resin compsn. suitably usable for a water-developable photosensitive layer for forming a letter press or lithographic plate is obtained by mixing (A) 100pts.wt. of perfectly or partially (50W100mol%) saponified polyvinyl acetate, (B) 20W200pts.wt. of a photopolymerizable monomer having en ethylenically unsatd. bond, and (C) 1W50pts.wt. obtained by homopolymerizing a polymerizable monomer, such as N,N-dimethylaminoethyl acrylate, having a group of general formula (1) and a group of general formula (2) (R1 is H or CH4, and R2, R3 are each 1W10C alkyl., or copolymerizing said monomer with another unsatd. monomer.