To provide a cutting device for a metal thin sheet drum, effectively utilizing material, and providing endless metal rings the end part of which is easily shaped.

The cutting device for a metal thin sheet drum circumferentially cuts the drum 2 formed of a metal thin sheet in a cylindrical form to form endless belt-shaped metal rings 7 into a predetermined width. It is provided with: a drum holding member 18 rotatably provided to hold the drum 2; and a pair of rotary cutters 5a and 5b abutting on the inner circumferential surface and the outer circumferential surface of the drum 2 held by the drum holding member 18 at a cutting position for cutting the drum. It may also be provided with a first rotation drive means 22 to drive and rotate the drum holding means 18, and a second rotation drive means to drive and rotate the cutters 5a and 5b.