To position and fix a clamp member on movable side to a predetermined position corresponding to size of a workpiece before fixing the workpiece, to simplify a mechanism of positioning and fixation and reduce a stroke of a fluid pressure cylinder.

In a vice 1, a guide fixation mechanism 13 capable of guiding the clamp member 4 on movable side for a movable base member 10 in a vice main body 2 so as to move in a predetermined direction and fixing it so as to release its fixation is composed of a first serration 53 formed on the movable base member 10, a second serration 54 formed on the clamp member 4 on movable side so as to mesh with the first serration 53, a guide groove 55, an anchor member 56 arranged slidably in the guide groove 55, and a plurality of bolts 57 capable of fixing the clamp member 4 on movable side to the anchor member 56 while the first serration 53 and the second serration 54 are meshed mutually.