The present invention, the drill bit is accommodated chuck； A driving part connected to the chuck to rotate the drill bit accommodated in the chuck, and the chuck part includes: a tightening jaw having a drill bit in a center and radially arranged to tighten the drill bit； A socket including a hollow hole in which a drill bit can be accommodated, and a plurality of tightening jaw receiving holes which are penetrated diagonally from a bottom surface and connected to the hollow hole to receive the tightening jaw； A guide portion including a tightening jaw guide hole configured to guide the movement of the tightening jaw by receiving at least a portion of one end of the tightening jaw； The first socket includes a hollow hole that may be provided therein, includes a screw thread formed on at least a part of the outer periphery of one end, and is configured to adjust the degree of tightening of the tightening jaw according to the back and forth movement according to the rotational motion. Adjusting member； A first body formed to surround at least a portion of an outer periphery of the first adjusting member, and including a screw thread formed to correspond to a screw thread of the first adjusting member on at least a portion of the inner periphery； A second body configured to support at least a portion of the socket and the guide portion in one direction, to insert at least a portion of the first body, and spaced apart from the first body by a predetermined distance； And a drill bit separation prevention part disposed on the tightening jaw and disposed on a surface in which the tightening jaw abuts the drill bit.본 발명은, 드릴 비트가 수용되는 척부； 상기 척부에 연결되어 상기 척부에 수용되는 드릴 비트를 회전작동시키는 구동부를 포함하고, 상기 척부는, 드릴 비트를 중앙에 두고 복수개가 방사형으로 배치되어 드릴 비트를 조임할 수 있는 조임 턱； 드릴 비트가 수용될 수 있는 중공홀, 및 하단면에서부터 사선으로 관통되어 상기 중공홀까지 연결되어 상기 조임 턱이 수용되도록 구성되는 복수의 조임 턱 수용홀을 포함하는 소켓； 상기 조임 턱의 일측 단부의 적어도 일부가 수용되어 상기 조임 턱의 이동을 가이드 할 수 있도록 구성되는 조임 턱 가이드홀을 포함하는 가이드부； 상기 소켓이 내부에 구비될 수 있는 중공홀을 포함하고 일측 단부 외주연의 적어도 일부에 형성되
