The present invention aims to provide methods for surface-modifying a rubber vulcanizate or a thermoplastic elastomer, which can cost-effectively impart a variety of functions, such as sliding properties or biocompatibility, according to the application. The present invention relates to a method for surface-modifying an object of a rubber vulcanizate or a thermoplastic elastomer, the method including: step 1 of forming polymerization initiation points A on the surface of the object and step 2 of radically polymerizing a non-functional monomer, starting from the polymerization initiation points A, to grow non-functional polymer chains, and further radically polymerizing a fluorine-containing functional monomer to grow fluorine-containing functional polymer chains.
