PURPOSE: To improve durability of a cord in a bead part, by constituting a carcass main unit from inner and outer layers and reducing compressive distortion of a carcass ply cord without causing the increase of kinds of the cord and the increase of material volume.

CONSTITUTION: A carcass 1 comprises inner and outer layer groups, and each group is equipped with a bead core 4. The inner layer carcass is arranged 5W 50% the total carcass, and at leat a sheet of layer with a large cord tilt angle is provided to the outer layer. While at least one sheet of a layer with a cord density larger than the cord density of the inner layer is provided to the outer layer, and a sheet of layer with 30% compression modulus of cord coating rubber corresponding to 1.2W2 times that of the inner layer is provided. In this way, compressive distortion of a carcass ply cord is reduced to improve durability of the cord without causing the cost up.