A tire tester comprising: a rotary member including a circumferential surface functioning as a traveling simulation road surface for a tire; a tire support mechanism configured to support the tire; and an actuator configured to advance and retreat at least one of the rotary member and the tire support mechanism with respect to the other such that the tire supported with the tire support mechanism is brought into contact with, pressed onto and brought apart from the circumferential surface of the rotary member, wherein the tire support mechanism includes: an axle extending in a second direction (x axis) perpendicular to a first direction (z axis) in which the rotary member or the tire support mechanism advances and retreats with the actuator, and supporting the tire to be rotatable such that a ground contact surface of the tire faces the circumferential surface of the rotary member; a main frame connected with the actuator; and a subframe supporting the axle, and movably attached to the main frame; characterized in that: the main frame and the subframe are movable together in the first direction (z axis) by the actuator, the subframe is movably attached to the main frame via at least one linear motion bearing such that a distance of the subframe from the main frame can be decreased and increased in the second direction (x axis) and/or a third direction (y axis); at least one load sensor (255c, 256c) provided between the main frame and the subframe and aligned with the axle; wherein the at least one load sensor (255c, 256c) is arranged to measure the forces in the second direction (x axis) and/or the third direction (y axis). a rotary member including a circumferential surface functioning as a traveling simulation road surface for a tire; a tire support mechanism configured to support the tire; and an actuator configured to advance and retreat at least one of the rotary member and the tire support mechanism with respect to the other such that the tire supported with the tire support mechanism is brought into contact with, pressed onto and brought apart from the circumferential surface of the rotary member, wherein the tire support mechanism includes: an axle extending in a second direction (x axis) perpendicular to a first direction (z axis) in which the rotary member or the tire support mechanism advances and retreats with the actuator, and supporting the tire to be rotatable such that a ground contact surface of the tire faces the circumferential surface of the rotary member; a main frame connected with the actuator; and a subframe supporting the axle, and movably attached to the main frame; characterized in that: the main frame and the subframe are movable together in the first direction (z axis) by the actuator, the subframe is movably attached to the main frame via at least one linear motion bearing such that a distance of the subframe from the main frame can be decreased and increased in the second direction (x axis) and/or a third direction (y axis); at least one load sensor (255c, 256c) provided between the main frame and the subframe and aligned with the axle; wherein the at least one load sensor (255c, 256c) is arranged to measure the forces in the second direction (x axis) and/or the third direction (y axis). an axle extending in a second direction (x axis) perpendicular to a first direction (z axis) in which the rotary member or the tire support mechanism advances and retreats with the actuator, and supporting the tire to be rotatable such that a ground contact surface of the tire faces the circumferential surface of the rotary member; a main frame connected with the actuator; and a subframe supporting the axle, and movably attached to the main frame; the main frame and the subframe are movable together in the first direction (z axis) by the actuator, the subframe is movably attached to the main frame via at least one linear motion bearing such that a distance of the subframe from the main frame can be decreased and increased in the second direction (x axis) and/or a third direction (y axis); at least one load sensor (255c, 256c) provided between the main frame and the subframe and aligned with the axle; wherein the at least one load sensor (255c, 256c) is arranged to measure the forces in the second direction (x axis) and/or the third direction (y axis).