Provided is a rubber-reinforcing steel cord that has superior productivity and is advantageous in reducing weight and improving bending resistance, as well as a conveyor belt that uses the rubber-reinforcing steel cord. A rubber-reinforcing steel cord 1 having a 1+6+(6+6) structure formed by twisting individual steel wires 2, 3, 4a, and 4b once in the same direction, a twist multiple of at least 9 and not greater than 14, and an outer diameter of not greater than 4 mm is used by being embedded in a rubber product.