To obtain a high-strength and inexpensive steel chord good in rubber infiltrativity, excellent in buckling resistance, and high in toughness and fatigue resistance, and to obtain a radial tire using these steel cords.

This steel cord for rubber reinforcement has the following characteristics: a flat open chord with 1×3 structure and the ratio of minor to major radius of 0.50-0.80; raw material for the wires constituting the steel ctord is carbon steel which contains 0.70-0.76wt.% carbon; tensile strength of each wire before laid into cord satisfies the relationship: Z≥-200(d)+365; and the ratio B/A is ≥0.930 (A is the collective tensile strength of the wires before laid into chord; B is the tensile strength of the cord after laid).