To rotate a rotary blade reversely when procedures for eliminating paper jam are taken and rotate it in the direction of cutting when it is desired to cut a sheet material manually by providing a release means which releases the transmission of driving force of a clutch to the rotary blade and enables manual rotation of the rotary blade at a position in the direction of shaft center of the rotary blade.

When it is desired to rotate a rotary blade 2 in the Q direction, namely, in the direction of anti-cutting or it is desired to rotate the rotary blade 2 in the P direction in order to perform manual cutting because paper jam occurs and the rotary blade 2 is stopped, a knob 15 is manually pressed in the arrow direction, namely, in the R direction against energizing force of a spring, and a gear 15a is meshed with a gear 14 attached on the rotary blade 2. A shaft 16 moves in the arrow direction, in the R direction and overrides on a bent part 4a of a lever 4, and the other end 4c of the lever 4 is disengaged from a claw part 3d of a spring clutch 3. Then, it is possible to rotate the rotary blade 2 freely in any direction without damaging the clutch 3 when the knob 15 is rotated manually because the gear 14 and the gear 15a are meshed each other.