PURPOSE: To provide a vice mouthpiece unit and a vice liner which can clamp even a material with burr.

CONSTITUTION: A vice mouthpiece unit 1 consists of a main body 3 in which a burr escape groove 2 is formed in the horizontal direction on the front of a substantially square body and fixed members 4 mounted on both sides of the main body 3 respectively so that the main body 3 is fixed on a mouthpiece 5a of a vice 5 in such a manner that its rear face is tightly close to a mouthpiece face 5b and it can be detached. Also, as for a vice liner 11, a burr escape cut-in section 12 is formed in a front side end section on a top surface of the substantially square body formed to a specific height in such a manner that its top surface is positioned within a scope of groove width of the burr escape groove 2 of the vice mouthpiece unit 1, and its front is brought into contact with a face having the burr escape groove 2 of the vice mouthpiece unit 1 for use.