PURPOSE: To reduce the vibration of a back plate and the noise generated from the back plate by constituting the end part coming into contact with an endless cutter of the back plate of a guide member made of a damping material.

CONSTITUTION: The back plate 50 supporting a part of an endless cutter C so as to press the same to a material to be cut is constituted by fixing elongated guide members 50B to the upper and lower end surfaces of a flat plate main body 50A. The material quality of the guide members 50B is constituted of a damping material such as a carbon fiber reinforced composite material or phosphor bronze and the friction resistance of the guide members 50B and the flaps of the cutter C is reduced and the chatter vibration of the back plate is reduced. Since the guide members 50B and the plate main body 50A are different in material quality, they are also different in resonance vibration frequency and vibration energy is absorbed at the bonding interfaces of both of them and the vibration of the back plate 50 is reduced to reduce noise.