Anon-pneumatic tire (1, 60) comprising: an attachment body attached to an axle; a cylindrical exterior body fitted onto the attachment body from the outside; a ring-shaped body (13, 62) configured to surround the exterior body from the outside in a tire radial direction; a plurality of connecting members (15, 63) configured to connect the exterior body and the ring-shaped body (13, 62) while allowing displacement therebetween; and a cylindrical tread member installed outside the ring-shaped body (13, 62), wherein an outer circumferential surface of the ring-shaped body (13, 62) is formed in a flat shape when seen in a cross-sectional view in the tire width direction, wherein the exterior body, the ring-shaped body (13, 62) and the plurality of connecting members (15, 63) are integrally formed of a synthetic resin material, characterised in that: an outer circumferential surface of the tread member has a plurality of curved surface sections (41, 42, 43) that are continuously formed in a tire width direction with no step difference and formed in a shape protruding outward in the tire radial direction when seen in a cross-sectional view in the tire width direction, the plurality of curved surface sections (41, 42, 43) have different radii of curvature (R1, R2, R3) when seen in a cross-sectional view in the tire width direction, in the plurality of curved surface sections (41, 42, 43), intermediate curved surface sections, which are disposed between a central curved surface section disposed at a central portion in the tire width direction and shoulder curved surface sections disposed outside in the tire width direction, have a radius of curvature larger than radii of curvature (R1, R3) of the other curved surface sections (41, 42) when seen in the cross-sectional view, and wherein the shoulder curved surface sections of the plurality of curved surface sections (41, 42, 43) have a radius of curvature smaller than radii of curvature (R1, R2) of the other curved surface sections (41, 42, 43) when seen in the cross-sectional view. an attachment body attached to an axle; a cylindrical exterior body fitted onto the attachment body from the outside; a ring-shaped body (13, 62) configured to surround the exterior body from the outside in a tire radial direction; a plurality of connecting members (15, 63) configured to connect the exterior body and the ring-shaped body (13, 62) while allowing displacement therebetween; and a cylindrical tread member installed outside the ring-shaped body (13, 62), wherein an outer circumferential surface of the ring-shaped body (13, 62) is formed in a flat shape when seen in a cross-sectional view in the tire width direction, wherein the exterior body, the ring-shaped body (13, 62) and the plurality of connecting members (15, 63) are integrally formed of a synthetic resin material, characterised in that: an outer circumferential surface of the tread member has a plurality of curved surface sections (41, 42, 43) that are continuously formed in a tire width direction with no step difference and formed in a shape protruding outward in the tire radial direction when seen in a cross-sectional view in the tire width direction, the plurality of curved surface sections (41, 42, 43) have different radii of curvature (R1, R2, R3) when seen in a cross-sectional view in the tire width direction, in the plurality of curved surface sections (41, 42, 43), intermediate curved surface sections, which are disposed between a central curved surface section disposed at a central portion in the tire width direction and shoulder curved surface sections disposed outside in the tire width direction, have a radius of curvature larger than radii of curvature (R1, R3) of the other curved surface sections (41, 42) when seen in the cross-sectional view, and wherein the shoulder curved surface sections of the plurality of curved surface sections (41, 42, 43) have a radius of curvature smaller than radii of curvature (R1, R2) of the other curved surface sections (41, 42, 43) when seen in the cross-sectional view. an outer circumferential surface of the tread member has a plurality of curved surface sections (41, 42, 43) that are continuously formed in a tire width direction with no step difference and formed in a shape protruding outward in the tire radial direction when seen in a cross-sectional view in the tire width direction, the plurality of curved surface sections (41, 42, 43) have different radii of curvature (R1, R2, R3) when seen in a cross-sectional view in the tire width direction, in the plurality of curved surface sections (41, 42, 43), intermediate curved surface sections, which are disposed between a central curved surface section disposed at a central portion in the tire width direction and shoulder curved surface sections disposed outside in the tire width direction, have a radius of curvature larger than radii of curvature (R1, R3) of the other curved surface sections (41, 42) when seen in the cross-sectional view, and wherein the shoulder curved surface sections of the plurality of curved surface sections (41, 42, 43) have a radius of curvature smaller than radii of curvature (R1, R2) of the other curved surface sections (41, 42, 43) when seen in the cross-sectional view.