To provide a mouthpiece of a vice with a structure for pressing a workpiece downward when the workpiece is held so as to assure the precision of a workpiece holding height, wherein the direction of a reference side of the workpiece also can be correctly defined.

A pair of mouthpieces of a vice includes a pair of a fixed mouthpiece 21 fixed to a fixing flange of the vice and a movable mouthpiece 1 fixed to a movable flange. The fixed mouthpiece 21 and the movable mouthpiece 1 have sawtooth surfaces 6 and 15 formed in the direction of moving claw blocks 3 and 3 downwardly with respect to base blocks 2 and 2 by holding reaction force of the vice. The fixed mouthpiece 21 includes end claws 22 fixed to the base block 2 at both breadthwise ends of the claw block 3. The front face 22a (work holding surface) of the end claw is leveled with the front face 3a of the claw block 3 to come into contact with the workpiece when the claw block 3 moves downward.