Provided are methods for surface-modifying a rubber vulcanizate or a thermoplastic elastomer, the methods forming a surface with a chemically fixed lubricant instead of resin coating which has drawbacks, such as that the coating is, for example, removed or peeled during the movement within a vessel, whereby the lubricity is reduced. 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 on a surface of the object, and step 2 of radically polymerizing a deliquescent monomer starting from the polymerization initiation points by irradiation with ultraviolet light having a wavelength within the range of 300 to 400 nm, to grow polymer chains on the surface of the object.
