PURPOSE: To simplify the work for attaching seal materials, obviate the necessary of resetting a central point when seal materials having different diameters are attached, the fix seal materials in a proper condition and perform accurate machining.

CONSTITUTION: In a vice 10, a pair of sliding parts 21 and 22 for forming a sandwitching part are engaged with both sides of two screw bars 12 and 13 on which the screw parts 12a(13a) and 12b(13b) are of reverse directions are provided on one end and the other end. Gear parts 15a and 16a are provided on the end of both screw bars 12 and 13 and a gear 17 is engaged with these gear parts 15a and 16a. Thus, the sliding parts 21 and 22 can be separated by rotating this gear 17.