To obtain the subject polymer having a gel content and swelling index in specific ranges, hardly causing adhesion to a roller and capable of providing a molding product having a proper hardness after molding by subjecting a polymerizable monomer to a γ-ray irradiation treatment.

This rubber polymer is obtained by carrying out a γ-ray irradiation treatment of a polymerizable monomer preferably by 20-140 kGy exposure preferably at 0-130°C, and has 40-80% gel content and 30-75 swelling index. The rubber polymer is preferably synthesized from ethylene and vinyl acetate, the ethylene and an acrylate, or the single acrylate. A molding product obtained by molding the rubber polymer is preferably a profile, a tube, an O-ring, a seal, a belt or the like. As the result, the rubber polymer not only having good processability such as the one capable of preventing a bubble formation, for example, in the injection molding, but also manifesting a filler allowance is expected.