A rubber composition consisting of 0.5 to 35% by weight of a conjugated diene-based (co)polymer rubber represented by the following formula or having an amino group and an alkoxysilyl group on a polymer chain and having a weight average molecular weight of 1,000 to 90,000 as measured by GPC (gel permeation chromatography), wherein the content of the primary amino group bonded to (co)polymer rubber is from 1 to 600 mmol/kg of (co)polymer rubber polymer, the content of the alkoxysilyl group bonded to the (co)polymer rubber is from 1 to 600 mmol/kg of (co)polymer rubber polymer, the amount of the conjugated diene used is from 50 to 95% by weight based on all monomers, and the content of the bonded aromatic vinyl compound bonded to the polymer chain is from 5 to 50% by weight based on the (co)polymer rubber, and 99.5 to 65% by weight of a conjugated diene-based (co) polymer rubber having a weight average molecular weight of 100,000 to 2,000,000 (with the proviso that + =100% by weight) in terms of polystyrene as measured by GPC (gel permeation chromatorgraphy): wherein the polymer rubber of a conjugated diene monomer is derived from 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene or chloroprene, wherein P is a (co)polymer chain comprising a conjugated diene alone or a conjugated diene and an aromatic vinyl compound, R 1 is an alkylene group having 1 to 12 carbon atoms, R 2 and R 3 are each independently an alkyl group having 1 to 20 carbon atoms or an aryl group, n is an integer of 1 or 2, m is an integer of 1 or 2, and k is an integer of 1 or 2, with the proviso that n+m+k is an integer of 3 or 4, wherein P, R 1, R 2 and R 3 have the same definitions as given for the above-mentioned formula, j is an integer of 1 to 3, and h is an integer of 1 to 3, with the proviso that j+h is an integer of 2 to 4. 0.5 to 35% by weight of a conjugated diene-based (co)polymer rubber represented by the following formula or having an amino group and an alkoxysilyl group on a polymer chain and having a weight average molecular weight of 1,000 to 90,000 as measured by GPC (gel permeation chromatography), wherein the content of the primary amino group bonded to (co)polymer rubber is from 1 to 600 mmol/kg of (co)polymer rubber polymer, the content of the alkoxysilyl group bonded to the (co)polymer rubber is from 1 to 600 mmol/kg of (co)polymer rubber polymer, the amount of the conjugated diene used is from 50 to 95% by weight based on all monomers, and the content of the bonded aromatic vinyl compound bonded to the polymer chain is from 5 to 50% by weight based on the (co)polymer rubber, and 99.5 to 65% by weight of a conjugated diene-based (co) polymer rubber having a weight average molecular weight of 100,000 to 2,000,000 (with the proviso that + =100% by weight) in terms of polystyrene as measured by GPC (gel permeation chromatorgraphy): wherein the polymer rubber of a conjugated diene monomer is derived from 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene or chloroprene, wherein P is a (co)polymer chain comprising a conjugated diene alone or a conjugated diene and an aromatic vinyl compound, R 1 is an alkylene group having 1 to 12 carbon atoms, R 2 and R 3 are each independently an alkyl group having 1 to 20 carbon atoms or an aryl group, n is an integer of 1 or 2, m is an integer of 1 or 2, and k is an integer of 1 or 2, with the proviso that n+m+k is an integer of 3 or 4, wherein P, R 1, R 2 and R 3 have the same definitions as given for the above-mentioned formula, j is an integer of 1 to 3, and h is an integer of 1 to 3, with the proviso that j+h is an integer of 2 to 4. wherein the polymer rubber of a conjugated diene monomer is derived from 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene or chloroprene, wherein P is a (co)polymer chain comprising a conjugated diene alone or a conjugated diene and an aromatic vinyl compound, R 1 is an alkylene group having 1 to 12 carbon atoms, R 2 and R 3 are each independently an alkyl group having 1 to 20 carbon atoms or an aryl group, n is an integer of 1 or 2, m is an integer of 1 or 2, and k is an integer of 1 or 2, with the proviso that n+m+k is an integer of 3 or 4, wherein P, R 1, R 2 and R 3 have the same definitions as given for the above-mentioned formula, j is an integer of 1 to 3, and h is an integer of 1 to 3, with the proviso that j+h is an integer of 2 to 4.