A heavy-duty tire comprising: a tread portion being provided with a pair of circumferentially and continuously extending zigzag central main grooves arranged on both sides of a tire equator, a pair of circumferentially and continuously extending zigzag shoulder main grooves each arranged between one of the central main grooves and one of tread edges (Te), a plurality of central lateral grooves connecting the pair of central main grooves and a plurality of middle lateral grooves connecting the central main groove with the shoulder main groove on both sides of the tire equator, thereby the tread portion comprising a central land portion in which a plurality of central blocks separated by the pair of central main grooves and the central lateral grooves are arranged in a circumferential direction of the tire, a pair of middle land portions in which a plurality of middle blocks separated by one of the central main grooves, one of the shoulder main grooves and the middle lateral grooves are arranged in a circumferential direction of the tire, and a pair of shoulder land portions separated between one of the shoulder main grooves and one of the tread edges (Te); each of the shoulder main grooves comprising a long side and a short side arranged alternately in a circumferential direction of the tire wherein the short side is inclined in an opposite direction to the long side and has a circumferential length shorter than that of the long side; each middle lateral groove connecting an outer zigzag corner of the central main groove with an inner zigzag corner of the shoulder main groove, wherein the outer zigzag corner protrudes on the side of the tread edge (Te), and wherein the inner zigzag corner protrudes on the side of the tire equator; and the middle blocks being provided with an inclined slot on a location facing one of the central lateral grooves through the central main groove, wherein the inclined slot has a depth increasing gradually toward the central main groove; characterized by each of the central main grooves comprising a long side and a short side arranged alternately in a circumferential direction of the tire wherein the short side is inclined in an opposite direction to the long side and has a circumferential length shorter than that of the long side; and each central lateral groove connecting the long sides of the pair of central main grooves. a tread portion being provided with a pair of circumferentially and continuously extending zigzag central main grooves arranged on both sides of a tire equator, a pair of circumferentially and continuously extending zigzag shoulder main grooves each arranged between one of the central main grooves and one of tread edges (Te), a plurality of central lateral grooves connecting the pair of central main grooves and a plurality of middle lateral grooves connecting the central main groove with the shoulder main groove on both sides of the tire equator, thereby the tread portion comprising a central land portion in which a plurality of central blocks separated by the pair of central main grooves and the central lateral grooves are arranged in a circumferential direction of the tire, a pair of middle land portions in which a plurality of middle blocks separated by one of the central main grooves, one of the shoulder main grooves and the middle lateral grooves are arranged in a circumferential direction of the tire, and a pair of shoulder land portions separated between one of the shoulder main grooves and one of the tread edges (Te); each of the shoulder main grooves comprising a long side and a short side arranged alternately in a circumferential direction of the tire wherein the short side is inclined in an opposite direction to the long side and has a circumferential length shorter than that of the long side; each middle lateral groove connecting an outer zigzag corner of the central main groove with an inner zigzag corner of the shoulder main groove, wherein the outer zigzag corner protrudes on the side of the tread edge (Te), and wherein the inner zigzag corner protrudes on the side of the tire equator; and the middle blocks being provided with an inclined slot on a location facing one of the central lateral grooves through the central main groove, wherein the inclined slot has a depth increasing gradually toward the central main groove;