A non-pneumatic tire (50, 70), comprising: an elastically deformable tire part which includes an inner cylinder attached to an axle shaft, an outer cylinder configured to surround the inner cylinder from the outside in a tire radial direction, and a linking member configured to link the inner cylinder to the outer cylinder; and a tread member externally fitted onto the outer cylinder, wherein an elastic modulus of a material forming the tread member is smaller than an elastic modulus of a material forming the tire part, an outer circumferential surface of the tread member is formed in a curved shape in which the outer circumferential surface thereof protrudes outward in the tire radial direction when viewed in a vertical cross-sectional view in both the tire width direction and a tire radial direction, and the outer cylinder includes an outer circumferential section positioned on a tire equatorial section, side sections positioned on both sides in a tire width direction with respect to the outer circumferential section, and a shoulder section configured to connect the outer circumferential section to the side sections, the outer circumferential section is formed in a straight linear form in which the outer circumferential section extends in the tire width direction and the shoulder section gradually extends inward in the tire radial direction as it goes outward in the tire width direction when viewed in the vertical cross-sectional view, and the shoulder section is formed in a curved shape in which the shoulder section protrudes outward in the tire width direction and outward in the tire radial direction when viewed in the vertical cross-sectional view, characterised in that: the shoulder section includes a plurality of circular arc sections (44, 44a, 44b) which are disposed in the tire width direction and have different curvatures when viewed in the vertical cross-sectional view, and in that in the plurality of circular arc sections (44, 44a, 44b), the curvatures gradually increase from the circular arc section positioned on an inner side in the tire width direction toward the circular arc section positioned on an outer side in the tire width direction. an elastically deformable tire part which includes an inner cylinder attached to an axle shaft, an outer cylinder configured to surround the inner cylinder from the outside in a tire radial direction, and a linking member configured to link the inner cylinder to the outer cylinder; and a tread member externally fitted onto the outer cylinder, wherein an elastic modulus of a material forming the tread member is smaller than an elastic modulus of a material forming the tire part, an outer circumferential surface of the tread member is formed in a curved shape in which the outer circumferential surface thereof protrudes outward in the tire radial direction when viewed in a vertical cross-sectional view in both the tire width direction and a tire radial direction, and the outer cylinder includes an outer circumferential section positioned on a tire equatorial section, side sections positioned on both sides in a tire width direction with respect to the outer circumferential section, and a shoulder section configured to connect the outer circumferential section to the side sections, the outer circumferential section is formed in a straight linear form in which the outer circumferential section extends in the tire width direction and the shoulder section gradually extends inward in the tire radial direction as it goes outward in the tire width direction when viewed in the vertical cross-sectional view, and the shoulder section is formed in a curved shape in which the shoulder section protrudes outward in the tire width direction and outward in the tire radial direction when viewed in the vertical cross-sectional view, characterised in that: the shoulder section includes a plurality of circular arc sections (44, 44a, 44b) which are disposed in the tire width direction and have different curvatures when viewed in the vertical cross-sectional view, and in that in the plurality of circular arc sections (44, 44a, 44b), the curvatures gradually increase from the circular arc section positioned on an inner side in the tire width direction toward the circular arc section positioned on an outer side in the tire width direction. the shoulder section includes a plurality of circular arc sections (44, 44a, 44b) which are disposed in the tire width direction and have different curvatures when viewed in the vertical cross-sectional view, and in that in the plurality of circular arc sections (44, 44a, 44b), the curvatures gradually increase from the circular arc section positioned on an inner side in the tire width direction toward the circular arc section positioned on an outer side in the tire width direction.