PURPOSE: To provide a pneumatic radial tire for heavy load, improved in durability in a bead part in preventing any separating at a carcass layer winding end in this bead part.

CONSTITUTION: This pneumatic radial tire or heavy load is so constituted that an end of a steel cord carcass layer 20 is wound up around a bead core 10, while a steel cord reinforced layer 30 is set up at the outside of a turnup part of this carcass part 20, and an end of a tire outside of this reinforced layer 30 is situated to be higher than the height of a rim flange and lower than a carcass layer winding end B, then an organic fiber reinforced layer 40 is set up at the outside of a tire outer side of this reinforced layer 30. In this constitution, a ratio f/g between thickness (f) ranging from a bead core outermost end A to a bead part outer surface and thickness (g) of the whole bead part is set to 0.05 to 0.4, while a ratio b/a between a distance (b) ranging rom the bead core outermost end A to a carcass layer winding end B and a distance (a) ranging from the bead core outermost end A to a rim flange contact end P of a bead part Z under normal load and normal internal pressure is set to be 1.5 to 2.0, respectively.