PURPOSE: To greatly improve poor strength of an unexposed blank plate and an exposed resin letterpress plate by using a photosensitive composition comprising a polyvinyl alcohol having an average molecular weight of ≥4000 and a compound having an radically polymerizable ethylenically unsaturated double bond and a photopolymerization initiator.

CONSTITUTION: When the average molecular weight of the polyvinyl alcohol is too low, an effect for enhancing the strength of the printing plate is lowered, so it is preferred to select the resin having an average molecular weight of ≥4000, further, ≥6000, especially, ≥8000, and most preferably, ≥10000. Any ethylenically unsaturated compound capable of undergoing radical polymerization by the photopolymerization initiator, such as polyvinyl alcohol type polymers, can be used and the ones good in compatibility with the photopolymerization initiator,k such as polyethylene glycol acrylate, are used. The photopolymerization initiator to be used is embodied by benzophenone and the like, thus permitting the strength of the printing plate material to be remarkably enhanced as compared with the conventional ones, while moderating deterioration of development speed.