A boring tool having a tool body (10) which has a pair of chip discharge flutes (11) formed in the peripheral surface thereof. A cutting edge (13) is formed on the edge line where the end relief surface of the tool body intersects the wall surface of each chip discharge flute which faces forwardly as viewed in the direction of the tool rotation. A first margin (15) is provided on the end of the land which is on the trailing side of the flute (11) as viewed in the tool rotation direction, while a second margin (17) is provided on the end of the land adjacent to the heel (16). The lands are provided with recesses (20) in the depths of each of which progressively increase from the first margin towards the second margin. A sub cutting edge (21) is formed on the edge line where the end relief surface meets the wall surface of the recess (20) which faces forwardly as viewed in the direction of the tool rotation.