A pneumatic tire having an enhanced cracking resistance at groove bottom, including at least one circumferential main groove 9 having such a sectional profile shape as including an axially inner wall portion 13, an inner arc portion 14 continuous with the inner wall portion 13, an axially outer wall portion 15 having a smaller length than the inner wall portion 13, an outer arc portion 16 continuous with outer wall portion 15, and a groove bottom portion 17 extending straight between the outer and inner arc portions while being inclined in a radially inward direction, in which the groove 9 has a maximum depth portion 18 on the tire equator side with respect to center position G1 of its width, and radius of curvature R1 of inner arc portion 14 and radius of curvature R2 of outer arc portion 16 satisfy the following relationships: R1≧0.6 mm and R2≧2×R1.