A tire comprising a tread portion, wherein the tread portion includes four circumferential grooves continuously extending in a tire circumferential direction between two tread ends (T1, T2), and five land portions demarcated by the four circumferential grooves, the two tread ends (T1, T2) are ends of a 50%-load ground-contact surface obtained when the tire is fitted on a normal rim with a normal internal pressure, 50% of a normal load is applied to the tire, and the tread portion is brought into contact with a flat surface at a camber angle of 0°, each of the five land portions is provided with no groove having a groove width greater than 2.0 mm, and is provided with only sipes, wherein "groove" means a groove in which, in a transverse cross-section thereof, a region where the distance between two groove walls is greater than 2.0 mm exceeds 50% of the total depth of the groove, and "sipe" means a small-width slit which has two inner walls extending in the tire radial direction and in which, in a transverse cross-section thereof, a region where the distance between the two inner walls is not greater than 2.0 mm is not less than 50% of the total depth of the slit, the five land portions include a shoulder land portion (11, 12) including the tread end (T1, T2), the four circumferential grooves include a shoulder circumferential groove (5, 6) adjacent to the shoulder land portion (11, 12), the shoulder land portion (11, 12) is provided with a plurality of shoulder sipes (20, 35) each extending from the shoulder circumferential groove (5, 6) to a position beyond the tread end (T1, T2), at least one of the shoulder sipes (20, 35) includes an inclined portion (21, 41) extending from the shoulder circumferential groove (5, 6) so as to be inclined relative to a tire axial direction, and an axial portion (22, 42) having an angle with respect to the tire axial direction smaller than the inclined portion (21, 41) and not greater than 10°, and the axial portion (22, 42) crosses the tread end (T1, T2), and the shoulder sipe (20, 35) includes a curved portion (23, 43) extending so as to be curved between the inclined portion (21, 41) and the axial portion (22, 42), characterized in that the curved portion (23, 43) has an arc shape having a radius of curvature of 10 to 40 mm. the tread portion includes four circumferential grooves continuously extending in a tire circumferential direction between two tread ends (T1, T2), and five land portions demarcated by the four circumferential grooves, the two tread ends (T1, T2) are ends of a 50%-load ground-contact surface obtained when the tire is fitted on a normal rim with a normal internal pressure, 50% of a normal load is applied to the tire, and the tread portion is brought into contact with a flat surface at a camber angle of 0°, each of the five land portions is provided with no groove having a groove width greater than 2.0 mm, and is provided with only sipes, wherein "groove" means a groove in which, in a transverse cross-section thereof, a region where the distance between two groove walls is greater than 2.0 mm exceeds 50% of the total depth of the groove, and "sipe" means a small-width slit which has two inner walls extending in the tire radial direction and in which, in a transverse cross-section thereof, a region where the distance between the two inner walls is not greater than 2.0 mm is not less than 50% of the total depth of the slit, the five land portions include a shoulder land portion (11, 12) including the tread end (T1, T2), the four circumferential grooves include a shoulder circumferential groove (5, 6) adjacent to the shoulder land portion (11, 12), the shoulder land portion (11, 12) is provided with a plurality of shoulder sipes (20, 35) each extending from the shoulder circumferential groove (5, 6) to a position beyond the tread end (T1, T2), at least one of the shoulder sipes (20, 35) includes an inclined portion (21, 41) extending from the shoulder circumferential groove (5, 6) so as to be inclined relative to a tire axial direction, and an axial portion (22, 42) having an angle with respect to the tire axial direction smaller than the inclined portion (21, 41) and not greater than 10°, and the axial portion (22, 42) crosses the tread end (T1, T2), and the shoulder sipe (20, 35) includes a curved portion (23, 43) extending so as to be curved between the inclined portion (21, 41) and the axial portion (22, 42), characterized in that the curved portion (23, 43) has an arc shape having a radius of curvature of 10 to 40 mm.