Provided is a pneumatic tire which can fundamentally prevent the phenomenon in which cracks are generated in the bottoms of grooves and the areas where the side walls of blocks meet the bottoms of grooves, can suppress irregular abrasion of the tread, can enhance the overall rigidity of the tread, and can also enhance the drainage performance. The pneumatic tire of the invention includes a tread, side walls and bead sections, with a large number of blocks compartmentalized by grooves being formed on the surface of the tread, and also includes reinforcing ribs that are positioned inside a groove and have their lower parts joined with the bottom of the groove, with one lateral surface of a reinforcing rib and one side wall of the groove being in contact.