Provided are methods for surface-modifying a rubber vulcanizate or a thermoplastic resin, which can provide chemically fixed surfaces showing low adsorption properties or selective adsorption properties with respect to proteins and cells, as well as excellent durability, instead of coatings which have drawbacks, such as that the performance is reduced due to separation or peeling of the coating. The present invention relates to a method for surface-modifying an object made of a rubber vulcanizate or a thermoplastic resin, the method including: a step 1 of forming polymerization initiation points on the surface of the object； and a step 2 of radically polymerizing a hydrophilic monomer starting from the polymerization initiation points by irradiation with UV light having a wavelength of 300 to 400 nm to grow polymer chains on the surface of the object.
