To clamp a work not to slip to the front when the work is clamped by a main stock vice jaw in angular cutting of the work.

A work W is clamped by a main stock vice 15 consisting of a main base stock vice jaw 15A and a main moving stock vice jaw 15B that is on the almost level surface and possible to turn freely. At this time, a roller 29 is journalled on the tip of the main moving stock vice jaw 15B. The main moving stock vice jaw 15B presses the work W diagonally and is clamped by the main base stock vice jaw 15A. Then, the component of a force in feeding direction by a clamping force of the main moving stock vice jaw 15B becomes very small owing to the reduction of frictional resistance by the rotation of the roller 29. Accordingly, the work W can be positioned at desired cutting position without slipping to the front of the material feeding direction.