PURPOSE: To prevent the occurrence of separation around a carcass up-ply end section and a drop in the durability of a carcass dot-ply section in the long-term use of a tire under a heavy load.

CONSTITUTION: The end of each up-ply 26 is dispersed and laid at both sides of a zone enclosed with the first perpendicular (m) orthogonal with the intermediate section of the up-ply 26 via an oppositional point 34 in a condition where internal pressure is fully applied and no load is acting, and the second perpendicular (n) orthogonal with the intermediate section of the up-ply 26 in a condition where internal pressure is fully applied and no load is acting, via such an oppositional point 36 as appearing in a case where internal pressure is fully applied and a load equal to 20% of a standard load is acting. Furthermore, the end of the up-ply 26 positioned at the radial outside of the zone is kept away from the internal end of a tire by a distance equal to 1.7 times or more of rim flange height H, and laid at the end of the tire inner than the third perpendicular P orthogonal with the intermediate section of the up-ply 26 via the maximum breadth position of the tire in a condition where internal pressure is fully applied and no load is acting.