A rubber composition having an excellent adhesion with a brass-plated wire and an excellent heat aging resistance of a vulcanite containing (A) 100 parts by weight of a diene-based rubber, (B) 0.1 to 10 parts by weight of, as a vulcanization accelerator, an amine salt compound of a carboxylic acid group-containing disulfide having the formula (I): and (C) 0.1 to 10 parts by weight of, as a vulcanization agent, a cyclic sulfide compound having the formula (V): wherein R is a substituted or unsubstituted C2-C20 alkylene group, a substituted or unsubstituted C2-C20 oxyalkylene group or an aromatic ring-containing alkylene group, x is an integer of 2-6 on average and n is an integer of 1-30.