Rubber component reinforcing-steel cord

Provided is a rubber component reinforcing-steel cord having improved corrosion resistance without increasing the weight thereof. The rubber component reinforcing steel cord 1 comprises a plurality of sheath strands 3 twisted around at least one core strand 2 having a plurality of steel filaments twisted therein, said sheath strands 3 comprising a plurality of steel filaments twisted therein. The core strand 2 and the sheath strands 3 comprise at least one core filament 2c, 3c, and a plurality of sheath filaments 2s, 3s wound therein. The relationship represented by formula (1), dcc > dcs ≥ dsc > dss, is satisfied, wherein the wire diameter of the core filaments 2c in the core strand 2 is dcc, the wire diameter of the sheath filament 2s is dcs, the wire diameter of the core filament 3c of the sheath strands 3 is dsc, and the wire diameter of the sheath filament 3s is dss.