A curable resin composition includes (A) a cationically polymerizable-compound, (B) a cationic photopolymerization initiator, and (C) an epoxidized polyisoprene containing an epoxy group at 0.15 to 2.5 meq/g in the molecule and having a number-average molecular weight of 15000 to 200000. The curable resin composition shows excellent elongation properties and high break elongation even in a cured state and can give a cured product having superior compatibility, transparency, flexibility and waterproofness. Accordingly, the composition is suitable for use as adhesives, coating agents, encapsulating materials, inks, sealing materials and the like.