 movable blade part 0 cooperate with each other to cut two or front and rear portions of the blade material 0 as shown in FIGS. 00 and 00, the front end 0a of the blade material 0 which is produced as a result of the cutting is not deformed but is maintained to the original adequate shape as shown in FIGS. 00A and 00B, but the rear end 0b of the blade material 0 which is produced as a result of the cutting is bent as shown in FIGS. 00C and 00D. In the blade material cutting device, also when the stationary edge for miter-cutting and the movable edge of the movable blade part 0 cooperate with each other to cut two or front and rear portions of the blade material 0 as shown in FIGS. 00 and 00, the front end 0a of the blade material 0 which is produced as a result of the cutting is not deformed but is maintained to the original adequate shape as shown in FIGS. 00A and 00B, but the rear end 0b of the blade material 0 which is produced as a result of the cutting is bent as shown in FIGS. 00C and 00D. 