To provide a holding device for an extremely thin metal plate capable of tightly holding an arbitrary-sized extremely thin metal plate at the central part of an XY stage with simple operation and in a short time.

The device is for holding a work piece in laser beam cutting work for the extremely thin metal plate such as a metal mask, wherein movable members 21, 22 gripping both ends of the extremely thin metal plate respectively are horizontally and slidably provided inside the rectangular fixing frame 20 mounted on an XY stage, a movable member 21 is connected to the fixing frame 20 with a stretcher 25, and the movable member 22 is connected to the movable member 21 through a sheave 28 provided on the fixing frame 20 by a pulling member 29, so that the extremely thin metal plate can be tightly held at the center part of the fixing frame 20 by attracting the movable member 21 with a stretcher 25.