A tyre comprising a tread portion including a tread surface which is to be in contact with a ground during running, wherein the tread portion is provided with a circumferential groove (3, 20, 30) extending continuously in a tyre circumferential direction, the circumferential groove (3, 20, 30) has a groove bottom and a pair of groove walls extending from the groove bottom to the tread surface in a tyre radial direction, the groove bottom is formed symmetrically with respect to a center line of the circumferential groove (3, 20, 30) in a plan view of the tread portion and includes a plurality of groove bottom protruding portions protruding outwardly in the tyre radial direction from a groove bottom reference surface defined as a surface parallel to the tread surface at a deepest position of a groove depth of the circumferential groove (3, 20, 30), each of the groove bottom protruding portions has a first groove bottom surface extending in the tyre radial direction and a second groove bottom surface having an angle (θ1) larger than that of the first groove bottom surface with respect to the tyre radial direction, each of the groove walls includes a plurality of groove wall protruding portions (11, 21, 31) each protruding toward an inner side of the circumferential groove (3, 20, 30) from a groove wall reference surface defined as a surface along the tyre circumferential direction at a widest position of a groove width of the circumferential groove (3, 20, 30), and each of the groove wall protruding portions (11, 21, 31) has a first groove wall surface extending in a tyre width direction and a second groove wall surface (13, 22, 32) having an angle with respect to the tyre width direction larger than that of the first groove wall surface, characterized in that i) the angle (θ1) between the second groove bottom surface and the tyre radial direction is in a range from 70 to 87 degrees, and ii) the second groove wall surface is formed by a flat surface having an angle (θ2) in a range from 3 to 20 degrees with respect to the tyre circumferential direction in the plan view of the tread portion or the second groove wall surface (22, 32) is formed by a curved surface. the tread portion is provided with a circumferential groove (3, 20, 30) extending continuously in a tyre circumferential direction, the circumferential groove (3, 20, 30) has a groove bottom and a pair of groove walls extending from the groove bottom to the tread surface in a tyre radial direction, the groove bottom is formed symmetrically with respect to a center line of the circumferential groove (3, 20, 30) in a plan view of the tread portion and includes a plurality of groove bottom protruding portions protruding outwardly in the tyre radial direction from a groove bottom reference surface defined as a surface parallel to the tread surface at a deepest position of a groove depth of the circumferential groove (3, 20, 30), each of the groove bottom protruding portions has a first groove bottom surface extending in the tyre radial direction and a second groove bottom surface having an angle (θ1) larger than that of the first groove bottom surface with respect to the tyre radial direction, each of the groove walls includes a plurality of groove wall protruding portions (11, 21, 31) each protruding toward an inner side of the circumferential groove (3, 20, 30) from a groove wall reference surface defined as a surface along the tyre circumferential direction at a widest position of a groove width of the circumferential groove (3, 20, 30), and each of the groove wall protruding portions (11, 21, 31) has a first groove wall surface extending in a tyre width direction and a second groove wall surface (13, 22, 32) having an angle with respect to the tyre width direction larger than that of the first groove wall surface, i) the angle (θ1) between the second groove bottom surface and the tyre radial direction is in a range from 70 to 87 degrees, and ii) the second groove wall surface is formed by a flat surface having an angle (θ2) in a range from 3 to 20 degrees with respect to the tyre circumferential direction in the plan view of the tread portion or the second groove wall surface (22, 32) is formed by a curved surface.