PURPOSE: To make the crack and the size growth produced in tread grooves checkable, by specifying angles made between both side edge parts of a groove being open to a meridian direction toward the side of a sidewall part from a shoulder part and the peripheral direction, for the sidewall of a tread shoulder part.

CONSTITUTION: Each groove 10 opened to an almost meridian direction toward the side of a sidewall part 2 from a tread shoulder part 1a is made up at an interval in a tire peripheral direction. And, among angles α and β made between a peridian direction contour 11 forming an edge part in the meridian direction of the groove 10 and a peripheral direction contour 12 forming an end edge part of the sidewall part 2 side, the angle β at the opposite side against peripheral direction force (a) by carcass cord waves shown in an arrow (a) is made to be larger than the angle α, and the angle β is set to 100° or more. Therefore, residual displacement tries to be restored by the charged inner pressure of a tire whereby any cracks can be surely prevented from occurring at a crossed part Rb between the meridian direction contour 11 and the peripheral direction contour 12 of the groove 10.