A heavy duty pneumatic tire comprising a plurality of block rows provided on a tread surface, each block row being composed of a plurality of blocks formed by a plurality of main grooves extending in a tire circumferential direction and a plurality of lateral grooves intersecting said main grooves, wherein a narrow block is provided, interposing a sub groove, in a position outside each block of block rows adjacent to an inner side of an outermost main groove in a tire width direction; and wherein a surface of said narrow block is formed to be circular-arc by setting a height of a center part of said narrow block surface in the tire circumferential direction to be equal to that of said tread surface and a height of both end parts of said narrow block surface to be lower than that of said tread surface by 1.5 to 2.5 mm.