PURPOSE: To prevent the central part of a tread from thinning and both the sides of the tread from unnecessarily thickening at the time of pressure vulcanization, by providing one or more recesses on both the sides of base rubber of the tread in the circumferential direction of the tire.

CONSTITUTION: The recesses 11, 12 are provided on the base rubber 8 between the side of the tread and a line J-J. Since the recesses 11, 12 are made by projections provided on the inside surface of a mold, the base rubber 8 is prevented by oblique parts corresponding to the walls 13, 14 of the recesses 11, 12 from flowing sidewards at the time of vulcanization. Thereby, the thickness of the part (b) of the tread is kept from increasing over a predetermined value.