A heavy-duty tire comprising a tread formed from a rubber composition containing a rubber component that includes 25 to 70% by mass of an isoprene-based rubber, 10 to 30% by mass of a butadiene rubber, and 20 to 55% by mass of a styrene-butadiene rubber, the rubber composition further containing, per 100 parts by mass of the rubber component, 10 to 70 parts by mass of a carbon black having a nitrogen adsorption specific surface area not less than 135 m 2 /g, wherein a ground-contact surface shape formed when the tread is pressed against a flat surface by application of a normal load in a normal state where the heavy-duty tire is mounted to a normal rim and inflated to a normal internal pressure and no load is applied to the heavy-duty tire, satisfies formulae and: 1.05 ≤ SL0 / SL70 ≤ 1.15 0.95 ≤ SL70 / SL97 ≤ 1.05 where SL0 represents a ground-contact length in a tire circumferential direction on a tire equator, SL70 represents a ground-contact length in the tire circumferential direction at a position that is apart from the tire equator in a tire axial direction by a distance that is 70% of a half ground-contact width of the tread, and SL97 represents a ground-contact length in the tire circumferential direction at a position that is apart from the tire equator in the tire axial direction by a distance that is 97% of the half ground-contact width of the tread, wherein the "normal rim" refers to a rim defined, in a standard system including a standard on which the tire is based, by the standard for each tire, and is the standard rim in the JATMA standard, the "Design Rim" in the TRA standard, or the "Measuring Rim" in the ETRTO standard, wherein the "normal internal pressure" refers to an air pressure defined by the aforementioned standard for each tire, and is the maximum air pressure in the JATMA standard, the maximum value indicated in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or the "INFLATION PRESSURE" in the ETRTO standard, and wherein the "normal load" refers to a load defined by the aforementioned standard for each tire, and is the maximum load capacity in the JATMA standard, the maximum value indicated in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or the "LOAD CAPACITY" in the ETRTO standard. a ground-contact surface shape formed when the tread is pressed against a flat surface by application of a normal load in a normal state where the heavy-duty tire is mounted to a normal rim and inflated to a normal internal pressure and no load is applied to the heavy-duty tire, satisfies formulae and: 1.05 ≤ SL0 / SL70 ≤ 1.15 0.95 ≤ SL70 / SL97 ≤ 1.05 where SL0 represents a ground-contact length in a tire circumferential direction on a tire equator, SL70 represents a ground-contact length in the tire circumferential direction at a position that is apart from the tire equator in a tire axial direction by a distance that is 70% of a half ground-contact width of the tread, and SL97 represents a ground-contact length in the tire circumferential direction at a position that is apart from the tire equator in the tire axial direction by a distance that is 97% of the half ground-contact width of the tread, wherein the "normal rim" refers to a rim defined, in a standard system including a standard on which the tire is based, by the standard for each tire, and is the standard rim in the JATMA standard, the "Design Rim" in the TRA standard, or the "Measuring Rim" in the ETRTO standard, wherein the "normal internal pressure" refers to an air pressure defined by the aforementioned standard for each tire, and is the maximum air pressure in the JATMA standard, the maximum value indicated in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or the "INFLATION PRESSURE" in the ETRTO standard, and wherein the "normal load" refers to a load defined by the aforementioned standard for each tire, and is the maximum load capacity in the JATMA standard, the maximum value indicated in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or the "LOAD CAPACITY" in the ETRTO standard.