Methods are provided for surface-modifying a rubber vulcanizate or a thermoplastic elastomer. The methods allow these objects to have a lubricating surface layer chemically fixed thereon and thus exhibit excellent lubricity and excellent lubricant durability, instead of having a resin coating which has drawbacks such as reduction in lubricity due to e.g. separation or peeling of the coating during movement within a vessel or tract. Further, the methods have good productivity and good economic efficiency. Included is a method for surface-modifying an object made of a rubber vulcanizate or a thermoplastic elastomer, the method including: step 1 of forming polymerization initiation points on a surface of the object； and step 2 of radically polymerizing a monomer starting from the initiation points by irradiation with UV of 300-400 nm to grow polymer chains on the surface so that a modification layer of 70-1200 nm thickness is formed on the surface.
