A pneumatic tire comprising: a plurality of land portions formed on a tread of the tire and partitioned by a plurality of circumferential grooves that extend in a tire circumferential direction, the plurality of land portions extending in the tire circumferential direction; and a plurality of widthwise grooves that are formed on the land portions and that extend in a tire widthwise direction, wherein in at least the outermost side circumferential grooves on outermost sides in the tire widthwise direction among the plurality of circumferential grooves , a plurality of ridge portions are formed in a spaced relation with each other in the tire circumferential direction such that the plurality of ridge portions project from a groove bottom of the outermost side circumferential grooves and cross the outermost side circumferential grooves with an angle with respect to the tire circumferential direction, at least one of the widthwise grooves on at least the shoulder land portions in a shoulder region on an outer side of one of the outermost side circumferential grooves has, on a groove bottom thereof, a widened groove portion having an increased groove width, characterized in that the widthwise groove on the shoulder land portion has a groove depth that gradually increases toward the outer side in the tire widthwise direction from a portion at which the widthwise groove is open to the outermost side circumferential groove to at least a tire widthwise direction position of a belt tire widthwise end edge positioned in the shoulder region of a belt of a belt layer arranged on an inner side in a tire diametrical direction of the tread . a plurality of land portions formed on a tread of the tire and partitioned by a plurality of circumferential grooves that extend in a tire circumferential direction, the plurality of land portions extending in the tire circumferential direction; and a plurality of widthwise grooves that are formed on the land portions and that extend in a tire widthwise direction, wherein in at least the outermost side circumferential grooves on outermost sides in the tire widthwise direction among the plurality of circumferential grooves , a plurality of ridge portions are formed in a spaced relation with each other in the tire circumferential direction such that the plurality of ridge portions project from a groove bottom of the outermost side circumferential grooves and cross the outermost side circumferential grooves with an angle with respect to the tire circumferential direction, at least one of the widthwise grooves on at least the shoulder land portions in a shoulder region on an outer side of one of the outermost side circumferential grooves has, on a groove bottom thereof, a widened groove portion having an increased groove width, characterized in that the widthwise groove on the shoulder land portion has a groove depth that gradually increases toward the outer side in the tire widthwise direction from a portion at which the widthwise groove is open to the outermost side circumferential groove to at least a tire widthwise direction position of a belt tire widthwise end edge positioned in the shoulder region of a belt of a belt layer arranged on an inner side in a tire diametrical direction of the tread . <EOS>