A photo-setting composition essentially consisting of:(A) 100 weight parts of a product prepared by esterifying a maleic anhydride adduct of a liquid polybutadiene with a hydroxyl compound;(B) 10 - 150 weight parts of one or more than one kind of unsaturated compound selected from the group consisting of a hydroxyl compound identified above, a di(meth)acrylate compound and a glycidyl monoester compound; and(C) 0.5 - 10 weight parts of a benzoinether compound.