To provide a thin sheet clamping device enabling easy removal at the time of removal of a thin sheet such as a printing plate and not causing coming-off or shift of it at the time of mounting.

In this thin sheet clamping device, a groove and a hole parallel to the center axis are formed in a cylindrical barrel. A clamping bar is inserted rotatably into the hole. One end of the folded thin sheet end is hooked on one wall of the groove. The other end is inserted into the other side wall of the groove and hooked on the protrusion of the clamping bar. The clamping bar is rotated to clamp the thin sheet. In this device, a stepped hole opened in the front of the protrusion is formed in the clamping bar. A metal fitting is fitted in the stepped hole and is energized so as to protrude from the opening and the protruding position is restricted. The fitting has a clearance to one wall restricting the protrusion at a position where the bar is rotated oppositely to the hooking direction. In the position where the bar is rotated in the hooking direction, the fitting is pressed against one wall by the spring, and further, a gap is formed between the fitting and the other wall. When the bar is rotated in an opposite direction from the position rotated in the hooking direction, the fitting is protruded along one wall.