A rubber composition, which comprises 100 parts by weight of an ethylene-alkyl acrylate copolymer rubber, 5-40 parts by weight of EPDM, 1-40 parts by weight of an α-olefin oligomer, 0.5-4 parts by weight of an organic peroxide cross-linking agent, 0.5-4 parts by weight of an amine-based vulcanizing agent, and 300-1,000 parts by weight of magnetic powder. The rubber composition is a rubber composition filled a magnetic powder at a high packing density, where an ethylene-alkyl acrylate copolymer rubber having amine vulcanizable groups as a binder, and effectively usable in rubber-bonded sensor magnets, etc., without any foaming at the time of vulcanization molding and with distinguished processabilities such as mold releasability, etc.