A drill driving apparatus comprising: - a tool driving mechanism configured to hold a tool (T) and apply a rotation operation and a feeding operation in a tool axis direction to the tool (T); and - a driving mechanism fixing instrument , having a through hole through which the tool (T) passes, configured to be inserted detachably into a guiding through hole in order to fix the tool driving mechanism to a drill jig in which the guiding through hole is formed, characterised in that : the driving mechanism fixing instrument comprises: - a first guide having a surface that contacts the drill jig , wherein the first guide is configured such that the surface moves away from the tool driving mechanism when the tool driving mechanism is rotated relatively in the opposite direction to the rotation direction of the tool (T); - a second guide that is adapted to widen in an interior of the guiding through hole in a radial direction of the guiding through hole when the tool driving mechanism is rotated relative to the first guide in the opposite direction to the rotation direction of the tool (T), wherein a plurality of slits having the tool axis direction as a length direction is provided in a work piece side end portion of the second guide ; and - a third guide that is fixed to the tool driving mechanism and is adapted to widen the second guide in the radial direction of the guiding through hole when the surface of the first guide that contacts the drill jig moves away from the tool driving mechanism , wherein a tapered portion for widening the work piece side of the second guide is provided on a work piece end side of the third guide . - a tool driving mechanism configured to hold a tool (T) and apply a rotation operation and a feeding operation in a tool axis direction to the tool (T); and - a driving mechanism fixing instrument , having a through hole through which the tool (T) passes, configured to be inserted detachably into a guiding through hole in order to fix the tool driving mechanism to a drill jig in which the guiding through hole is formed, - a first guide having a surface that contacts the drill jig , wherein the first guide is configured such that the surface moves away from the tool driving mechanism when the tool driving mechanism is rotated relatively in the opposite direction to the rotation direction of the tool (T); - a second guide that is adapted to widen in an interior of the guiding through hole in a radial direction of the guiding through hole when the tool driving mechanism is rotated relative to the first guide in the opposite direction to the rotation direction of the tool (T), wherein a plurality of slits having the tool axis direction as a length direction is provided in a work piece side end portion of the second guide ; and - a third guide that is fixed to the tool driving mechanism and is adapted to widen the second guide in the radial direction of the guiding through hole when the surface of the first guide that contacts the drill jig moves away from the tool driving mechanism , wherein a tapered portion for widening the work piece side of the second guide is provided on a work piece end side of the third guide . <EOS>