To provide a workpiece vice that supports a workpiece with high rigidity, while holding the workpiece based on the center of the workpiece.

A screw rod for opening/closing a cap has right and left screws on both axially sides, and a nut member of a base is screwed to the right and left screws. A guide plate slender in the screw axial direction is fixed to the cap base on each side of the screw rod. The guide plate fixed to one cap base and the guide plate fixed to the other cap base are slidably fitted to guide grooves of a base, while flat surfaces of the guide plates opposite to each other are slidably brought into surface contact with each other. A guide bar in the screw axial direction is formed between the inner guide plate and the internal inner wall surface of the guide groove, and between the outer guide plate and the external outer inner wall surface of the guide groove.