A lactone-modified epoxy (meth)acrylate resin is disclosed as is a hardenable resin composition which includes the lactone-modified epoxy resin. The lactone-modified epoxy (meth)acrylate resin is obtained by addition polymerizing 3 to 95 parts by weight of a lactone to 97 to 5 parts by weight of an epoxy (meth)acrylate resin at the whole or a part of the secondary hydroxy groups thereof. The hardenable resin composition comprises (A) 5 to 95 parts by weight of the above referred to lactone-modified epoxy (meth)acrylate resin, (B) 95 to 5 parts by weight of a vinyl compound having an ethylenically unsaturated bond, and (C) 0 to 10 parts by weight of a photosensitizer.