To provide a rotation balance adjusting flange mechanism for avoiding vibration of a cutting blade rotating at a high speed, and simplifying labor of adjusting balance by eliminating malfunction caused when a mark is put by a magic pen.

A fixing nut includes a plurality of weight housing parts in which balancing weights can be inserted from a surface serving as a front end face at prescribed intervals in the circumferential direction when the fixing nut holds a cutting blade in cooperation with a fixed flange, and includes display parts indicating the positions of respective weight housing parts in the vicinity of the weight housing parts on the surface.