Provided is a pneumatic radial tire including a carcass layer composed of a carcass ply 12 and a spiral belt layer 26 composed of steel cords wound spirally substantially in parallel with each other to a tire equator surface. When the ratio of spacing R1 between adjacent steel cords of the spiral belt layer 26 is shown by R1=(50−E×ds)/50, the ratio of spacing R1 is 0.45 or less as well as the total sectional area S of the steel cords applied per 50 mm width of the spiral belt layer is 7.5 mm2 or less (E shows the number of steel cords applied per 50 mm width of the spiral belt layer, and ds shows the diameter (mm) of each steel cord). The number of steel cords E applied per 50 mm of width ranges from 66 to 200.