A pneumatic tire is provided in the tread portion with a main groove and an axial groove. The groove-sidewall surface on each side of the main groove is formed by a circular-arc-like surface having a radius R1 of curvature and being convex to the groove center side. The groove-sidewall surface on each side of the axial groove is formed by a circular-arc-like surface having a radius R2 of curvature and being convex to the groove center side. The radius R2 of curvature of the groove-sidewall surface of the axial groove is more than the radius R1 of curvature of the groove-sidewall surface of the main groove.