Disclosed is a radial tire having a cap ply manufactured with a polyethylene terephthalate dip cord. The radial tire includes: a pair of parallel bead cores; at least one radial carcass ply wound around the bead cores; one or more inclined belt layers layered on the outer circumference of the carcass ply; and one or more cap ply layers layered in the circumferential direction of a tire on the outer circumference of the inclined belt layers, wherein the cap ply includes a dip cord manufactured using a yarn comprising 90 mol % or more of polyethylene terephthalate, and the dip cord has a shrinkage of 3.0-4.0%, a strength of 2.5-3.0 g/d at an elongation of 5%, a breaking strength of 6.5-7.5 g/d, and a dimensional stability index of 5.8-6.5.