Abstract: A heavy duty pneumatic radial tire comprises at least one carcass ply reinforced with steel cords substantially arranged at an angle of 90.degree. with respect to an equator of the tire and wound around a bead core from inside of the tire toward outside thereof. In this tire, the steel cord is made from steel wires each having a tensile strength of 330-400 kg/mm.sup.2 and a cementite lamellar distance of 120-190 .ANG., a residual stress of whose is compression stress at a depth within a range of 1/10 to 1/5.5 of a wire diameter from the surface of the steel wire.