PROBLEM TO BE SOLVED: To provide an artificial joint instrument which is used in a surgery to replace a part or whole of the joint with an artificial joint and has an attachment member detachably fitted in an insertion member, moreover, can suppress the insertion member and the attachment member from separating from each other after the fixed state of the attachment member and the insertion member is cancelled against the intention of the operator.SOLUTION: In the artificial joint instrument (1), a fixing member (4) attached to a recessed groove (31) of an attachment member (3) is pressure-welded to an insertion part (21) of an insertion member (2) inserted into an insertion hole (32) of the attachment member (3) to fix the insertion part (21) to the attachment member (3). The fixing member (4) is a resin member comprising a plurality of fixing pieces (41, 42) divided in a circumferential direction.
