To suppress or prevent the generation of CBU(carcass breakup) failure of bead parts of a pneumatic radial tire for heavy load so as to improve durability of beads.

A pneumatic radial tire is provided with a lateral pair of bead cores arranged at bead parts, and a radial carcass extended from a crown part to both bead parts via both side wall parts and moored to the bead parts after winding around the bead cores. The bead core 1 is formed by binding a plurality of metallic wires, coated with insulating rubber, in a step row state, and the radial carcass 2 is formed of a plurality of cord layers embedded in coating rubber. In this case, thickness of a rubber member such as insulating rubber or coating rubber interposed between the bead core 1 and the radial carcass 2 in a radially inner area at least from the maximum width position of the bead core 1 in cross section including a rotation axis of the tire is set thicker on the mold lower side than on the mold upper side at the time of vulcanization of the tire.