A coupling agent for rubber/carbon black, comprising at least one compound selected among: - the sulfide compounds represented by the following chemical formula: in which each A represents O, S, NH or NR; each R represents a linear or branched alkyl or alkenyl group having 1 to 6 carbon atoms, or a cyclic alkyl or alkenyl group having 3 to 6 carbon atoms, and when A is NR, the plurality of R's on a condensed aromatic heterocyclic ring may be the same as or different from each other; n represents an integer from 1 to 6; and x represents an integer from 1 to 4, - bis(benzimidazolyl-2)methyl sulfide, - 2,2'-bis(benzimidazolyl-2)ethyl sulfide, - 2,2'-bis(benzimidazolyl-2)ethyl disulfide, - 2,2'-bis(benzimidazolyl-2)ethyl trisulfide, - 2,2'-bis(benzimidazolyl-2)ethyl tetrasulfide, - 3,3'-bis(benzimidazolyl-2)propyl disulfide, - 3,3'-bis(benzimidazolyl-2)propyl trisulfide, - 3,3'-bis(benzimidazolyl-2)propyl tetrasulfide, - 4,4'-bis(benzimidazolyl-2)butyl disulfide, - 4,4'-bis(benzimidazolyl-2)butyl trisulfide, - 4,4'-bis(benzimidazolyl-2)butyl tetrasulfide, - 5,5'-bis(benzimidazolyl-2)pentyl disulfide, - 5,5'-bis(benzimidazolyl-2)pentyl trisulfide, - 5,5'-bis(benzimidazolyl-2)pentyl tetrasulfide, - 6,6'-bis(benzimidazolyl-2)hexyl disulfide, - 6,6'-bis(benzimidazolyl-2)hexyl trisulfide, - 6,6'-bis(benzimidazolyl-2)hexyl tetrasulfide, - 2,2'-bis(1-methylbenzimidazolyl-2)ethyl disulfide, - 3,3'-bis(1-methylbenzimidazolyl-2)propyl disulfide, - 2,2'-bis(1-ethylbenzimidazolyl-2)ethyl disulfide, - 3,3'-bis(1-ethylbenzimidazolyl-2)propyl disulfide, - 3,3'-bis(1-n-propylbenzimidazolyl-2)propyl disulfide, - 3,3'-bis(1-isopropylbenzimidazolyl-2)propyl disulfide, - 3,3'-bis(1-tert-butylbenzimidazolyl-2)propyl disulfide, - 2,2'-bis(benzoxazolyl-2)ethyl disulfide, - 2,2'-bis(benzoxazolyl-2)ethyl trisulfide, - 2,2'-bis(benzoxazolyl-2)ethyl tetrasulfide, - 3,3'-bis(benzoxazolyl-2)propyl disulfide, - 4,4'-bis(benzoxazolyl-2)butyl disulfide, - 5,5'-bis(benzoxazolyl-2)pentyl disulfide, - 6,6'-bis(benzoxazolyl-2)hexyl disulfide, - 2,2'-bis(benzothiazolyl-2)ethyl disulfide, - 2,2'-bis(benzothiazolyl-2)ethyl trisulfide, - 2,2'-bis(benzothiazolyl-2)ethyl tetrasulfide, - 3,3'-bis(benzothiazolyl-2)propyl disulfide, - 4,4'-bis(benzothiazolyl-2)butyl disulfide, - 5,5'-bis(benzothiazolyl-2)pentyl disulfide, and - 6,6'-bis(benzothiazolyl-2)hexyl disulfide. - the sulfide compounds represented by the following chemical formula: in which each A represents O, S, NH or NR; each R represents a linear or branched alkyl or alkenyl group having 1 to 6 carbon atoms, or a cyclic alkyl or alkenyl group having 3 to 6 carbon atoms, and when A is NR, the plurality of R's on a condensed aromatic heterocyclic ring may be the same as or different from each other; n represents an integer from 1 to 6; and x represents an integer from 1 to 4, - bis(benzimidazolyl-2)methyl sulfide, - 2,2'-bis(benzimidazolyl-2)ethyl sulfide, - 2,2'-bis(benzimidazolyl-2)ethyl disulfide, - 2,2'-bis(benzimidazolyl-2)ethyl trisulfide, - 2,2'-bis(benzimidazolyl-2)ethyl tetrasulfide, - 3,3'-bis(benzimidazolyl-2)propyl disulfide, - 3,3'-bis(benzimidazolyl-2)propyl trisulfide, - 3,3'-bis(benzimidazolyl-2)propyl tetrasulfide, - 4,4'-bis(benzimidazolyl-2)butyl disulfide, - 4,4'-bis(benzimidazolyl-2)butyl trisulfide, - 4,4'-bis(benzimidazolyl-2)butyl tetrasulfide, - 5,5'-bis(benzimidazolyl-2)pentyl disulfide, - 5,5'-bis(benzimidazolyl-2)pentyl trisulfide, - 5,5'-bis(benzimidazolyl-2)pentyl tetrasulfide, - 6,6'-bis(benzimidazolyl-2)hexyl disulfide, - 6,6'-bis(benzimidazolyl-2)hexyl trisulfide, - 6,6'-bis(benzimidazolyl-2)hexyl tetrasulfide, - 2,2'-bis(1-methylbenzimidazolyl-2)ethyl disulfide, - 3,3'-bis(1-methylbenzimidazolyl-2)propyl disulfide, - 2,2'-bis(1-ethylbenzimidazolyl-2)ethyl disulfide, - 3,3'-bis(1-ethylbenzimidazolyl-2)propyl disulfide, - 3,3'-bis(1-n-propylbenzimidazolyl-2)propyl disulfide, - 3,3'-bis(1-isopropylbenzimidazolyl-2)propyl disulfide, - 3,3'-bis(1-tert-butylbenzimidazolyl-2)propyl disulfide, - 2,2'-bis(benzoxazolyl-2)ethyl disulfide, - 2,2'-bis(benzoxazolyl-2)ethyl trisulfide, - 2,2'-bis(benzoxazolyl-2)ethyl tetrasulfide, - 3,3'-bis(benzoxazolyl-2)propyl disulfide, - 4,4'-bis(benzoxazolyl-2)butyl disulfide, - 5,5'-bis(benzoxazolyl-2)pentyl disulfide, - 6,6'-bis(benzoxazolyl-2)hexyl disulfide, - 2,2'-bis(benzothiazolyl-2)ethyl disulfide, - 2,2'-bis(benzothiazolyl-2)ethyl trisulfide, - 2,2'-bis(benzothiazolyl-2)ethyl tetrasulfide, - 3,3'-bis(benzothiazolyl-2)propyl disulfide, - 4,4'-bis(benzothiazolyl-2)butyl disulfide, - 5,5'-bis(benzothiazolyl-2)pentyl disulfide, and - 6,6'-bis(benzothiazolyl-2)hexyl disulfide.