A pneumatic tire comprises: a tread rubber having a Shore A hardness of not more than 65 degrees at 20 degrees C.; a tread portion provided with at least one circumferential row of blocks having circumferential edges adjacent to lateral grooves; each of the circumferential edges having a mean inclination angle of 0 to 60 degrees with respect to the tire axial direction; sidewalls of the lateral grooves on one side in the tire circumferential direction each comprising a first upper slope extending from the top of the adjacent block to a first point at a depth h1, while inclining at an angle .alpha.1, and a first lower slope extending from said first point towards the groove bottom, while inclining at an angle .alpha.2 smaller than the angle .alpha.1,; the remaining sidewalls of the lateral grooves on the other side each comprising a second upper slope extending from the top of the adjacent block to a second point at a different depth h2 than said depth h1, while inclining at an angle .beta.1, and a second lower slope extending straight from the second point towards the groove bottom, while inclining at an angle .beta.2 smaller than the angle .beta.1; and the lateral grooves comprising a portion (A) in which the depth h1 is more than the depth h2 but not more than 0.8 times the lateral groove depth, and a portion (B) in which the depth h2 is more than the depth h1 but not more than 0.8 times the lateral groove depth.