A groove bottom is formed symmetrically about a center line of a circumferential groove in a tread plan view and includes groove bottom protruding portions protruding radially outwardly from a groove bottom reference surface parallel to a tread surface at a deepest position of a groove depth. Groove bottom protruding portions have a first groove bottom surface extending radially and a second groove bottom surface having an angle larger than the first groove bottom surface. Groove walls include groove wall protruding portions protruding toward an inner side of the circumferential groove from a groove wall reference surface as a circumferential surface at a widest position of a groove width. The groove wall protruding portions each has a first groove wall width surface and a second groove wall surface having an angle larger than the first groove wall width surface.