A circumferential groove has a groove bottom and a pair of groove walls. Groove bottom includes groove bottom protruding portions protruding radially outwardly from a groove bottom reference surface and having a first groove bottom surface extending radially. The first groove bottom surface includes a first surface portion on one side of a center line of the circumferential groove and a second surface portion positioned on the other side, and an angle between them is 20° to 170°. The groove wall includes groove wall protruding portions protruding toward an inside of the circumferential groove from a groove wall reference surface defined as a circumferential surface at a widest groove width position of the circumferential groove and having a first groove wall width surface 12 extending in a tyre width direction and a second groove wall surface having an angle larger than the first groove wall width surface.