A pair of stopper members are mounted on shafts of an actuator in such a manner that stopper members sandwich a table. By making the table come into contact with these stopper members, a stop operation and a determination of a stop position of the table are carried out. To be more specific, the stop operation and the determination of the stop position of the table is carried out by using adjusting bolts which are respectively mounted on the stopper members. Furthermore, an impact which occurs when the adjusting bolts and the table come into contact with each other is attenuated by shock absorbers which are respectively mounted on said stopper members.