A pneumatic radial tire including a carcass composed of at least one carcass layer extending toroidally between a left-and-right pair of bead cores; a tread portion which is arranged on the outside in the tire radial direction of a crown region of the carcass to form a ground contacting portion; and a belt composed of two belt layers which is arranged between the tread portion and the crown region of the carcass to form a reinforcing portion. A reinforcing material constituting the belt layer is a bundle formed by arranging two cords in pairs; and, letting the diameter of a filament constituting the cord a (mm), the interval between the adjacent bundles as an expected value is increased by a/4 (mm) or larger compared to the interval represented by using the circumcircle of the cord.