A pneumatic tire having on-snow performance improved by increasing traction performance on snow-covered road with maintaining dry grip performance high, and comprising tread surface 2 having at least one circumferential main groove 3 in an outer region 2o facing outward of a vehicle, the circumferential main groove 3 being a straight groove wherein ridge lines 21 at which groove wall surfaces 20 intersect with the tread surface 2 extend straight, each groove wall surface 20 comprising a gently-inclined upper wall surface 20U extending from the ridge line 21 at an angle θ1 of 40 to 60° with respect to a normal line to tread surface 2 and a steeply-inclined lower wall surface 20L extending to groove bottom 22 at an angle θ2 smaller than the angle θ1, and the lower wall surface 20L including projections 23 which are disposed at intervals in the circumferential direction and have a triangular cross section with slope surface 23S extending from lower end Ue of the upper wall surface 20U to groove bottom 22 at an angle θ3 which is not greater than the angle θ1 but is greater than the angle θ2.