A steel cord for reinforcing rubber article having a 1×n structure composed of a plurality of steel filaments stranded in the same direction at the same stranding pitch, the number of the steel filaments being 6 to 12 and the diameter of the steel filaments being 0.08 to 0.21 mm. In the pneumatic radial tire having a carcass, as a framework, extending toroidally between a pair of bead parts, with a crown part of the carcass being reinforced with a belt layer, the above-described steel cord for reinforcing rubber article is applied to a cord constituting the belt layer.