A heavy duty radial tire having an aspect ratio of at most 50 %, the outer diameter growth of which at tread shoulder portions is suppressed to improve uneven wear resistance and durability, and wherein belt layer 7 includes a radially outermost belt ply 10, belt cords of belt plies 9 except the outermost belt ply 10 are arranged at an angle of 10 to 70 DEG with respect to the circumferential direction, and the outermost belt ply 10 is made of a spiral wind ply 12 in which a ribbon-like strip 11 having steel cords is spirally wound in the circumferential direction, and the outermost belt ply 10 has a main body portion 10A which extends between ply folding back positions Po located on both sides of the tire equator, and fold portions 10B which are folded back at the ply folding back positions Po toward the tire equator in a U shape, in which the width CWa of the main body portion 10A is from 70 to 80 % of a tread ground contact width TW, and the width CWb of each fold portion 10B is at least 5.0 mm and is at most 0.5 times the width CWa.