A pneumatic tire includes main grooves 1 extending substantially in a circumferential direction R of the tire, transverse grooves 2 connecting adjacent main grooves, and blocks 3 formed by adjacent main grooves and adjacent transverse grooves. Each block 3 has an acute corner portion 3a and an obtuse corner portion 3b and also has a groove side extending along the main groove 1 between the acute corner portion 3a and the obtuse corner portion 3b. An inclination angle a1 of the groove side increases from the obtuse corner portion 3b toward the acute corner portion 3a. An extending direction 1a of the main groove 1 at a tread surface level is inclined toward one side of the main groove 1 with respect to the circumferential direction R of the tire, while an extending direction of the main groove 1 at a groove bottom level is inclined toward the other side.