To obtain a photosensitive composition capable of being developed with an aqueous alkaline solution, presenting an abrasion-resistant plane printing plate having a strong printing resistance, having a wide range of developing conditions without giving stains during printing, excellent in coupling performance, suitable for ball pen writing, having sensitivity and stability during preservation and little deterioration in performances such as sensitivity after exposure and the like.

In the photosensitive composition containing a water insoluble and aqueous alkaline solution-soluble vinyl polymer-based high molecular compound and o-naphthoquinone diazide, the vinyl polymer-based high molecular compound is a copolymer containing at least one species of each of (A) a monomer compound having an active imino group expressed by a specific general formula and (B) a monomer unit derived from a monomer compound having an onium group expressed by a specific general formula.