PURPOSE:The titled composition, containing a specific photopolymerizable unsaturated compound, specific photopolymerization initiator and epoxy resin, capable of preventing occurrence of electromigration and having small deterioration in insulation resistance between conductor circuits after moisture resistance test as well as high resolution. CONSTITUTION:A composition containing (A) a photopolymerizable unsaturated compound, e.g. trimethylolpropane, etc., having at least two terminal ethylene groups, (B) a photopolymerization initiator capable of generating free radicals by actinic rays, optimally benzyldimethyl ketal, etc., and (C) an epoxy resin, preferably polyglycidyl ether of polyhydric phenol. Cured films (resists) of the aimed composition are formed on a part except a part for forming a conductor circuit on an insulation substrate or a part except a through-hole part on a substrate having the conductor circuit provided thereon to afford a circuit board. 5-20pts.wt. component (C) is preferably blended in 100pts.wt. total of the components (A) and (C). USE:Suitable for production processes of circuit boards by an additive method.