A pneumatic tire is provided in the tread portion (2) with a circumferential groove (3, 3b, 3c) extending continuously in the tire circumferential direction and having a pair of oppositely opposed groove walls (6). The circumferential groove (3, 3b, 3c) is provided in at least one of the groove walls (6) with radial grooves (9) arranged along the longitudinal direction of the circumferential groove (3). The radially outer end (9o) of the radial groove (9) is positioned in a range (a1) of from 0 to 20% of the depth (GDt) of the circumferential groove. The radially inner end (9i) of the radial groove (9) is positioned in a range (a2) of from 80 to 100% of the depth (GDt) of the circumferential groove. The radial groove has an opening width (g) of not less than 1.0 mm, but not more than 6.0 mm.