A pneumatic tire having improved performance on ice and wet road surfaces without degradation of steering stability on dry road surfaces. The pneumatic tire includes a tread portion, side wall portions, bead portions, a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire width direction provided in the tread portion, a plurality of blocks partitioned by the circumferential and lateral grooves, and a plurality of sipes extending in the tire width direction in each block. At least some sipes include a main body part located centrally in the block width direction, and a deep-bottomed communicating portion that communicates with the circumferential groove adjacent to the block and has a depth not less than 50% the depth of the circumferential groove, and mutually mating convex and concave portions are formed locally in opposing surfaces in the deep-bottomed communicating portion.