To suppress flat spot without impairing driving stability.

The pneumatic radial tire 1 has a carcass 6 comprising two sheets of carcass plies 6i, 6o; a belt layer arranged at an outer side in a radial direction of the carcass 6; and a bead apex 8 and has a flatness ratio of 60-80%. The carcass plies 6i, 6o include a thick thread carcass cord comprising an organic fiber having thickness of 1,400 dtex/2 or thicker. In the regular state, in the inner carcass ply 6i arranged at the inner side, an outer end 6it of a folded part 6b1 is positioned at an outer side in the radial direction than the tire maximum width position M. In the outer carcass ply 6o, an outer end 6ot of the folding pard 6b2 is positioned left from the tire maximum width position M to the inner side in the tire radial direction by a distance a of 10-70 mm. An outer end 8t of the bead apex 8 is positioned left from the tire maximum width position M to the inside in the tire radial direction by a distance b of 5-55 mm. Further, the difference (a-b) of the distances is 5 mm or longer.