A pneumatic tire comprising a tread portion provided with a unidirectional tread pattern having an intended tire rotational direction, the tread portion provided with: a plurality of axial grooves each extending between tread edges (Te) and curved convexly toward the intended tire rotational direction; a pair of connecting grooves disposed one on each side of the tire equator, and disposed between every two of the circumferentially adjacent axial grooves so as to connect therebetween; a circumferential groove disposed along the tire equator (c), and disposed between every two of the circumferentially adjacent axial grooves so as to connect therebetween; a pair of crown blocks formed between every two of the circumferentially adjacent axial grooves, and divided by the two connecting grooves and one circumferential groove, wherein each crown block has a substantially trapezoidal configuration, and an axial width (Wa) gradually decreasing toward the intended tire rotational direction; and a pair of shoulder blocks formed between every two of the circumferentially adjacent axial grooves, and disposed axially outside the respective crown blocks, on each side of the tire equator (c), the axially outer ends of the crown blocks are positioned axial outside the axially inner ends of the shoulder blocks, wherein each of the axial grooves comprises a first groove segment extending across the tire equator and a pair of second groove segments on both sides thereof in the tire axial direction, and each second groove segment defines an axially outer oblique edge of one of the crown blocks, each of the shoulder blocks is provided with a shoulder axial groove having an inner end connected to one of the second groove segments and an outer end opened at the adjacent tread edge (Te), characterized in that the shoulder axial groove comprises an inside segment having said inner end and an outside segment having a groove width more than a groove width of the inside segment, and the outside segment has an inclination angle (θ5) of not more than 45 degrees with respect to the tire axial direction. a plurality of axial grooves each extending between tread edges (Te) and curved convexly toward the intended tire rotational direction; a pair of connecting grooves disposed one on each side of the tire equator, and disposed between every two of the circumferentially adjacent axial grooves so as to connect therebetween; a circumferential groove disposed along the tire equator (c), and disposed between every two of the circumferentially adjacent axial grooves so as to connect therebetween; a pair of crown blocks formed between every two of the circumferentially adjacent axial grooves, and divided by the two connecting grooves and one circumferential groove, wherein each crown block has a substantially trapezoidal configuration, and an axial width (Wa) gradually decreasing toward the intended tire rotational direction; and a pair of shoulder blocks formed between every two of the circumferentially adjacent axial grooves, and disposed axially outside the respective crown blocks, on each side of the tire equator (c), the axially outer ends of the crown blocks are positioned axial outside the axially inner ends of the shoulder blocks, wherein each of the axial grooves comprises a first groove segment extending across the tire equator and a pair of second groove segments on both sides thereof in the tire axial direction, and each second groove segment defines an axially outer oblique edge of one of the crown blocks, each of the shoulder blocks is provided with a shoulder axial groove having an inner end connected to one of the second groove segments and an outer end opened at the adjacent tread edge (Te), characterized in that the shoulder axial groove comprises an inside segment having said inner end and an outside segment having a groove width more than a groove width of the inside segment, and the outside segment has an inclination angle (θ5) of not more than 45 degrees with respect to the tire axial direction.