To provide an auxiliary tool for drilling capable of effectively preventing run-out of a drill tool in drilling a hole, capable of easily positioning a drill edge with respect to a punched recess, and capable of enhancing machining efficiency and working efficiency.

A chuck part 4 for clamping the drill tool 3 is mounted on a tip of a drill body 2, and a run-out preventing member 5 covering the drill tool 3 along the longitudinal direction and being slidable is provided on the chuck part 4. The run-out preventing member 5 is formed by connecting cylindrical members 5a comprising a metal or resin material divided into a plurality of pieces so as to have smaller diameter sequentially in the longitudinal direction in a telescopic manner, and a hook shaped fitting part 6 mutually fittable is formed on the connecting part of the cylindrical member 5a. An elastic member 7 such as a spring interposed in the run-out preventing member 5, and a tip side of the run-out preventing member 5 is usually energized to the tip side of the drill tool 3 by the elastic member 7.