Provided are a hydrocarbon resin and a method of preparing the same, wherein thermal polymerization of a diolefin and an olefin is performed, thus obviating a catalyst removal process, material supply problems can be solved, and a hydrogenated hydrocarbon resin can be prepared using a catalyst, which is inexpensive and is easy to handle, thereby realizing a yield and a preparation process that enable real-world application thereof. The hydrogenated hydrocarbon resin prepared by the method of the invention has excellent compatibility and a low specific viscosity, and can thus be efficiently used as a tackifier or an adhesive in a variety of fields.