A pneumatic tire having a rotation direction specified in one direction. The tread surface has a main groove extending on the equatorial plane of the tire, right and left first inclination grooves extending in an inclined manner from the main groove toward the reverse rotation direction of the tire, and right and left second inclination grooves disposed on the opposite sides of the main groove. The right and left second inclination grooves are disposed at symmetrical positions with respect to the equatorial plane of the tire. Blocks are formed on the opposite sides of the main groove by the main groove, right and left first inclination grooves and right and left second inclination grooves. The blocks include right and left first blocks defined by tire rotation direction side portions of the second inclination grooves, main groove and first inclination grooves, and right and left second blocks defined by tire reverse rotation direction side portions of the second inclination grooves, main groove and first inclination grooves. First main groove portions between the right and left first blocks are less in width than second main groove portions between the right and left second blocks.