Abstract: The present invention relates to a reactive vinyl polymer having (meth)acryloyl groups on the side chains obtained by radical-copolymerizing a monofunctional (meth)acrylate with a polyfunctional (meth)acrylate under specific conditions in a solvent as well as a method for preparing the same. In order to prevent the occurrence of gelation during the copolymerization, a long chain alkyl group or the like is introduced into the monofunctional (meth)acrylate to control a crosslinking reaction while making use of the steric effect of the long chain alkyl group or the like. The vinyl polymer of the present invention is effective for use as a photo hardenable and thermo setting gluing agent or adhesive and a resin for gluing agents and adhesives, further it serves as a functional polymeric material and thus can be incorporated into other resins.