This invention relates to a rubber composition capable of improving fracture properties and wear resistance of a tire, and more particularly to a rubber composition formed by compounding a non-compatible polymer blend, which comprises at least two rubber components and forms a polymer phase A and a polymer phase B, with a block copolymer comprising a block-a composed of the same monomer unit as a monomer unit forming the polymer phase A and a block-b composed of the same monomer unit as a monomer unit forming the polymer phase B, wherein at least one of the rubber components has at least one functional group.