To provide a device capable of stably supplying a wire to a welding machine by braking the unwinding of the wire bundle mounted in a drum.

In this braking device for unwinding the wire bundle in a mechanism supplying the unwound wire to the welding machine while unwinding the wire bundle consisting of the winding of a metal wire, which is mounted in the drum, the braking device consists of an annular disk 1 to be mounted on the wire bundle in the drum. It is equipped with a flexible body 2 protruded on the outer edge of the disk 1, and is equipped with a small wing 3 for wire guide and a flexible plate 5 on the inner edge of the disk 1. The flexible body 2 is formed in a size so that it comes into close contact with the inside surface of the drum while being bent, if necessary.