Abstract: PCT No. PCT/JP78/00026 Sec. 371 Date July 17, 1979 Sec. 102(e) Date July 16, 1979 PCT Filed Nov. 15, 1978 PCT Pub. No. WO79/00300 PCT Pub. Date May 31, 1979A boring needle device for treatment of a dental root canal has a boring needle useful upon treating a dental root canal. The needle can be adjusted, without resort to any special adjustment expedient, to a boring effective needle length which is corresponding to a depth of the canal preliminarily determined by separate means. The needle is secured at the proximal end to a grip member which is caused to stepwisely minutely slide relative to a sleeve member whereby a length of the needle projecting from the sleeve member can be finely adjusted by a determined minute distance.