PROBLEM TO BE SOLVED: To provide an instrument for a bone surgery, for which guide accuracy of a surgical instrument is improved.SOLUTION: The instrument 10 for the bone surgery includes a guide member 3 for guiding the surgical instrument 2 to a bone 1 and an instrument body 11 for guiding the guide member 3. The instrument body 11 includes a fixing part 12 and an insertion guide part 13 where an insertion part 19 for inserting and guiding the guide member 3 is provided through. The insertion guide part 13 is divided into a guide part 14 and a positioning part 20 by a first slit 15. The positioning part 20 is divided into two parts 22A and 22B by a second slit 21 which divides the insertion part 19 in the direction of inserting the guide member 3 from the upper end part 23A of the positioning part 20. The instrument 10 for the bone surgery is provided with a tightening member 25 for moving both of the two parts 22A and 22B of the positioning part 20 in the direction of the center axis Y of the positioning part 20.
