A shank attachment device (A, B) configured to attach a drill (50, 51) to a rotating portion of a drill device and comprising an arbor and a shank, the arbor being detachably attachable to the rotating portion, the arbor and the shank being detachably attachable to each other, and the shank being detachably attachable to the drill (50, 51), wherein: with the shank attached to the arbor, a stopper member disposed on the arbor engages with a stopper groove formed on a side surface of the shank to stop a movement of the shank in an axial direction away from the arbor; wherein the arbor includes an attachment shaft that is configured to be attached to the rotating portion of the drill device, an enlarged diameter portion is formed at a tip end portion of the attachment shaft, and wherein the shank is configured to be detachably attached to a shank attachment hole formed on the arbor, characterized in that a first engaging portion formed on the arbor engages with a first engaged portion formed on the shank to enable a rotational torque of the arbor to be transmitted to the shank; and the shank contacts the arbor to stop the movement of the shank in the axial direction toward the arbor, the enlarged diameter portion is detachably coupled to a base body of the arbor by a screw (11a, 12b); a center drill attachment hole communicated with the shank attachment hole is formed on the base body of the arbor; a fixing screw hole including an internal screw thread on an inner peripheral surface thereof is formed to extend from an outer peripheral surface of the base body to a center of the center drill attachment hole in a direction perpendicular to the center drill attachment hole; a fixing screw threadedly engages with the fixing screw hole such that a tip end thereof is able to project into the center drill attachment hole; and in that the enlarged diameter portion covers from outside at least a part of the fixing screw, which threadedly engages with the fixing screw hole, to prevent the fixing screw from falling out to an outside of the base body. with the shank attached to the arbor, a stopper member disposed on the arbor engages with a stopper groove formed on a side surface of the shank to stop a movement of the shank in an axial direction away from the arbor; wherein the arbor includes an attachment shaft that is configured to be attached to the rotating portion of the drill device, an enlarged diameter portion is formed at a tip end portion of the attachment shaft, and wherein the shank is configured to be detachably attached to a shank attachment hole formed on the arbor, characterized in that a first engaging portion formed on the arbor engages with a first engaged portion formed on the shank to enable a rotational torque of the arbor to be transmitted to the shank; and the shank contacts the arbor to stop the movement of the shank in the axial direction toward the arbor, the enlarged diameter portion is detachably coupled to a base body of the arbor by a screw (11a, 12b); a center drill attachment hole communicated with the shank attachment hole is formed on the base body of the arbor; a fixing screw hole including an internal screw thread on an inner peripheral surface thereof is formed to extend from an outer peripheral surface of the base body to a center of the center drill attachment hole in a direction perpendicular to the center drill attachment hole; a fixing screw threadedly engages with the fixing screw hole such that a tip end thereof is able to project into the center drill attachment hole; and in that the enlarged diameter portion covers from outside at least a part of the fixing screw, which threadedly engages with the fixing screw hole, to prevent the fixing screw from falling out to an outside of the base body.