PURPOSE: To reduce the weight and improve the fatigue resistance of steel cord by parallelly arranging plural core element wires, winding an element wire having a diameter smaller than that of the core element wire around the core element wires and using the obtained steel cord having flat cross section as the reinforcing material for a composite rubber material.

CONSTITUTION: Two or more core element wires 2 parallelly arranged in a row or ≥5 core element wires parallelly arranged in two or more rows and having bent parts 4 on a part or total of the element wires in longitudinal direction are wound with an element wire 3 having a diameter (ds) satisfying the formula 0.8dc≥ds (dc is diameter of the element wire 2) to form a steel cord 1 having flat cross section. When the steel cord 1 is used as a reinforcing material for a composite rubber material such as tire and belt and embedded in the rubber in such a manner as to keep the flat part of the tire or the belt parallel to the broad face of the steel cord 1, the bent parts 4 of the core element wires 2 contribute to getting desired elongation characteristics and a rubber-intrusion hole 5 is formed by the bent part 4 to improve the bonding of the rubber and the steel cord 1.