An airless tire has a cylindrical tread ring 2 having a ground-contacting surface 21, a hub disposed on the radially inside of the tread ring 2 and fixed to an wheel shaft, and spokes connecting between the tread ring 2 and the hub. The tread ring 2 has a side wall 22 continued from the ground-contacting surface 21 and forming a ring side surface. The side wall 22 has a supporting portion 23 which, when the tread ring 2 alone is horizontally laid on a horizontal surface H, contacts with a horizontal surface H and supports the tread ring 2 so that a ring axis A2 is oriented in a direction perpendicular to the horizontal surface H.