A rubber-reinforcing cord (30) according to the present invention includes: a reinforcing fiber or reinforcing fiber bundle (21); a first coating (22) provided to cover the reinforcing fiber or reinforcing fiber bundle (21); and a second coating (31) provided to cover the first coating (22) and be located at the outer surface of the rubber-reinforcing cord (30). The first coating (22) includes: first rubber including nitrile-based rubber as a main component; and a first crosslinking agent. The second coating (31) is a coating different from the first coating (22) and includes: second rubber consisting essentially of nitrile-based rubber; and a second crosslinking agent. The nitrile-based rubber is at least one selected from nitrile rubber, hydrogenated nitrile rubber, carboxylated nitrile rubber, and carboxylated hydrogenated nitrile rubber.