PURPOSE:To enable total 6 surfaces of a work once mounted to be worked by adding a vertical surface rotation indexing function to a horizontal rotation indexing function which is the standard operation of a machine tool. CONSTITUTION:A box-type angle plate 37 is provided on an index table when a work clamp 36 is mounted on a machine tool. Also, a hollow shaft 40 rotatably attached to the box-type angle plate 37 is incorporated in a housing hole 38 of said angle plate 37 through two ball bearings 39. To a stepped portion 41 of the hollow shaft 40 is fixedly attached a large gear 42 for indexing rotatably the hollow shaft 40 and a face plate 44 for mounting a work is mounted on the front end face 43 of said shaft 40. A work clamping means is constituted from these hollow shafts 40 and the face plate 44. Thus, after the work is mounted on the work clamp 36 and on the index table of the machine tool, working is carried out.