A belt layer 7 of a heavy load radial tire includes second and third belt plies 7B and 7C in which belt cords are arranged at an angle in a range of 10 to 45.degree. with respect to a circumferential direction of the tire, and a fourth belt ply 7D which is disposed outside of the second and third belt plies 7B and 7C and which is spirally wound in the circumferential direction of the tire. When ply widths of the belt plies 7B to 7D are defined as W2 to W4 and a tread ground-contact width is defined as Tw, the following relations are established: 0.85Tw.ltoreq.W2, 0.85Tw.ltoreq.W3, (W2-W3).gtoreq.14 mm, W4.gtoreq.40 mm. A distance K between a tire equator and an outer end of the fourth belt ply 7D is in a range of 35% to 40% of the tread ground-contact width Tw. A reinforcing rubber layer 10 having the maximum thickness T1 of not less than 3.0 mm and a complex elastic modulus E* of in a range of 6.0 to 12.0 MPa is disposed between outer ends of the second and third belt plies 7B and 7C.