PURPOSE: To ensure machining accuracy, by piling a set of tilt stands with an equal tilt angle of upper and lower surfaces, relatively rotating the both tilt stands and high rigidly adjusting a tilt angle of a rotary table on the tilt stand.

CONSTITUTION: A worm shaft 41, in which upper and lower surfaces 41a, 41b are provided with an equal tilt angle to a bearing 40, is supported by the bearing 40 equipped with a thrust receiving surface 40b tilted for a setting surface 40a. A rotary surface table 45, integraly formed with one tilt stand 47 of the set of tilt stands 47, 48, having an equal tilt angle of upper and lower surfaces, is bearing supported by the upper surface of the worm shaft 41, and an index table, mounting a work 1, is rotatably and fixably mounted to the upper surface of the other tilt stand 48. Gears are formed in the periphery of the tilt stands 47, 48, and meshed to axially shifting gears 53, 55, then the tilt stands are integrally or relatively rotated. The worm shaft 41 is rotated, and a tilt angle of oscillating motion due to relative rotation of the tilt stands 47, 48 can be adjusted by tilting a rotary shaft of the work 1.