To solve the problems of a conventional small-diameter drill for printed board wherein though the accuracy of hole location during boring is improved, the accuracy of hole location is lowered when three or more sheets of printed boards are stacked and bored together to raise a boring efficiency, which may have a structural problem, the drill is clogged with chips, and the quantity of 2,000 of boards can be board at the maximum.

A thinning edge 5 is formed at a chisel edge section 3 formed at the drill end section 2 of a small-diameter drill body 1 for printed board having a diameter of 3.175 mm or shorter. A chip discharge groove 9 is formed along a drill spiral groove. By forming the thinning edges 5 symmetrically to the chisel edge, a total of four edges comprising two sheets of the main edges 6 of the drill and two sheets of newly formed thinning edges 5 are provided to the small-diameter drill.