The present invention relates to a photosensitive compound comprising a vinyl polymer compound which is insoluble in water and soluble in an aqueous alkaline solution and o-naphthoquinonediazide compound, wherein said vinyl polymer compound is a copolymer comprising at least one monomer unit derived from monomer compound (A): a compound having an alkaline-soluble group represented by general formula (I), (II) or (III) as defined in the specification, and at least one monomer unit derived from monomer compound (B): (meth)acrylate having poly(oxyalkylene) chain. A lithographic printing plate prepared from a presensitized plate having a photosensitive layer of said photosensitive compound of the present invention shows improvement of abrasion resistance, printing durability, chemical resistance, development latitude, and contamination property.