PURPOSE: To prevent a protrusion of a work to the outer side even though the work is thin, and to improve the position accuracy, by approaching opposing surfaces each other in the condition to provide round bar members along the inclined surfaces of the grooves of the opposing surfaces of a vise respectively, and holding the work by pressing downward by the round bar members.

CONSTITUTION: When a work W is held, the interval between a pair of opposing plates 51 and 61 is expanded, and the work W is loaded on a holding table S. Then, by using a trapezoidal screw 4, the opposing surfaces 51 and 61 are approached until round bar members 7 held to grooves 52 and 62 are abutted to the holding end faces of the work, so as to hold the work W. As a result, a downward force to separate the round rod members 7 from the front end sides of the opposing surfaces 51 and 61 is received by the upper side inclined surfaces of the grooves 52 and 62. Consequently, the round bar members 7 is to press the work W downward and to held it, and a protrusion of the work is prevented.