A tire vulcanizing method for vulcanizing a green tire using a vulcanization mold including a tread mold for molding a tread portion of the green tire and a pair of side molds for molding a pair of sidewall portions of the green tire, the tire vulcanizing method comprising: a mounting step of mounting the green tire within the vulcanization mold in a state where the vulcanization mold is opened; and a vulcanizing step of vulcanizing the green tire in a closed state where the tread mold and the pair of side molds are set at predetermined reference positions, wherein the mounting step includes a green tire pressing step (S1c) of, after the green tire is mounted within the vulcanization mold, moving at least one of the pair of side molds such that the pair of side molds are closer to each other in a tire axial direction than the reference positions thereof, to reduce a width in the tire axial direction between the pair of sidewall portions of the green tire, and a positioning step (S1d) of, after a predetermined time elapses from the green tire pressing step (S1c), moving the pair of side molds to the reference positions and stopping the pair of side molds, characterized in that the tire vulcanizing method comprises a tread mold moving step (S1e) of, after the positioning step (S1d), moving the tread mold in a tire radial direction to position the tread mold at the reference position thereof, and a division position between the pair of side molds and the tread mold is within 15% of a tire cross-sectional height inward and outward in the tire radial direction from a maximum width position of a vulcanized tire. a mounting step of mounting the green tire within the vulcanization mold in a state where the vulcanization mold is opened; and a vulcanizing step of vulcanizing the green tire in a closed state where the tread mold and the pair of side molds are set at predetermined reference positions, wherein the mounting step includes a green tire pressing step (S1c) of, after the green tire is mounted within the vulcanization mold, moving at least one of the pair of side molds such that the pair of side molds are closer to each other in a tire axial direction than the reference positions thereof, to reduce a width in the tire axial direction between the pair of sidewall portions of the green tire, and a positioning step (S1d) of, after a predetermined time elapses from the green tire pressing step (S1c), moving the pair of side molds to the reference positions and stopping the pair of side molds, a green tire pressing step (S1c) of, after the green tire is mounted within the vulcanization mold, moving at least one of the pair of side molds such that the pair of side molds are closer to each other in a tire axial direction than the reference positions thereof, to reduce a width in the tire axial direction between the pair of sidewall portions of the green tire, and a positioning step (S1d) of, after a predetermined time elapses from the green tire pressing step (S1c), moving the pair of side molds to the reference positions and stopping the pair of side molds, characterized in that the tire vulcanizing method comprises a tread mold moving step (S1e) of, after the positioning step (S1d), moving the tread mold in a tire radial direction to position the tread mold at the reference position thereof, and a division position between the pair of side molds and the tread mold is within 15% of a tire cross-sectional height inward and outward in the tire radial direction from a maximum width position of a vulcanized tire.