In order to make the expansion incision while simply preventing the bone from tilting backward, the bone expansion device (1) includes: a pair of swinging members which are connected in a swingable manner with the axis (A) of the pivoting portion (2) as an axis； A pair of slitting members (5, 6) are inserted into the incision formed in the bone, and are pulled apart by the relative swing of the swinging member (3, 4) with the axis (B1, B2) as the axis To expand the incision； the opening and closing mechanism (7, 8) makes the swinging member (3, 4) swing relative to the axis (A), wherein each of the opening and closing members (5, 6) ) Has a contact surface (5b, 6b), and the contact surface (5b, 6b) is in contact with the cutting surface contacting the bone in a state where the split member (5, 6) is inserted into the cutout in a specific insertion direction, and The distance between the contact surfaces (5b, 6b) has a shape that is greater on the back side of the bone than on the front side.為了一邊簡易地防止骨頭後傾一邊進行擴張切口，骨頭擴張裝置(1)具備：一對擺動部件，其係以樞轉部(2)的軸線(A)為軸而呈可擺動之方式連接；一對開闔部件(5, 6)，其插入於形成於骨頭中的切口中，並且藉著該擺動部件(3, 4)以該軸線(B1, B2)為軸所作的相對擺動而拉開距離，藉此擴張該切口；開闔機構(7, 8)，其使該擺動部件(3, 4)以該軸線(A)為軸而作相對擺動，其中，各該開闔部件(5, 6)具有接觸面(5b, 6b)，於該開闔部件(5, 6)以特定插入方向插入該切口的狀態下，該接觸面(5b, 6b)係與接觸該骨頭的切割面接觸，且該接觸面(5b, 6b)之間的距離係具有於該骨頭的後側大於前側之形狀。
