The present invention aims to provide a surface modification method for a rubber vulcanizate or a thermoplastic elastomer, which can impart excellent sliding properties and durability against repeated sliding motion and can allow the surface to maintain the sealing properties, without using expensive self-lubricating plastics. The present invention relates to a surface modification method for modifying a rubber vulcanizate or a thermoplastic elastomer as an object to be modified, the method including: Step 1 of allowing a photopolymerization initiator to be adsorbed on a surface of the object to be modified and Step 2 of radical polymerizing monomers, starting from the adsorbed photopolymerization initiator, by irradiation with UV light at a wavelength of 300 nm to 400 nm to grow polymer chains on the surface of the object to be modified.
