A pneumatic radial tire having a tire component consisting of a steel cord, wherein the steel cord has (a) a 1+N structure in which N pieces of sheath filaments are twisted around a core filament permanently formed into a spiral shape in a cord longitudinal direction, (b) a flat cross-sectional shape, (c) an open structure where the sheath filaments have clearances between adjoining filaments at the cord cross section, (d) the core filament cut into clearances between the filaments, and (e) the spiral direction of the core filament aligned with the twisting direction of the sheath filaments.