The present invention provides a method for modifying the surface of a vulcanized rubber or thermoplastic elastomer, the method not only imparting excellent sliding properties, durability in repetitions of sliding, and performances with respect to prevention of protein adsorption and aggregation, without requiring the use of an expensive resin having self-lubricating properties, but also enabling the rubber or elastomer to retain satisfactory sealing properties over a long period. Also provided is a surface-modified elastic object, at least some of the surface of which has been modified by the surface modification method, the elastic object being for use, for example, as gaskets for syringes or in medical instruments such as catheters and diagnosis devices for blood/body fluid.The surface modification method is for a vulcanized rubber or thermoplastic elastomer as an object to be modified, and comprises: step 1 in which polymerization initiation sites are formed on a surface of the object to be modified step 2 in which a monomer is radical-polymerized using the polymerization initiation sites as starting points, thereby growing polymer chains on the surface of the object to be modified and step 3 in which the grown polymer chains are irradiated with electron beams.La présente invention concerne un procédé de modification de la surface dun caoutchouc ou dun élastomère thermoplastique vulcanisé, le procédé conférant non seulement dexcellentes propriétés de glissement, de durabilité dans les répétitions de glissement, et dexcellentes performances en ce qui concerne la prévention de ladsorption et lagrégation des protéines, sans nécessiter lutilisation dune résine coûteuse ayant des propriétés auto-lubrifiantes, mais permettant également au caoutchouc ou à lélastomère de conserver des propriétés détanchéité satisfaisantes sur une longue période. Linvention concerne également un objet élastique modifié en surface, dont au moins une partie de la surface a été modifiée par
