A guillotine cutter (1) of the invention is provided with a pressing block driving mechanism (6) positioning a pressing block (5) at a standby position which is spaced upwardly from a sheet bundle (10), a first operating position pressing the sheet bundle by a first pressing force, and a second operating position pressing the sheet bundle by a second pressing force which is larger than the first pressing force. The pressing block is carried by a rod (61) through a compression spring (62) at the standby position, the pressing block is supported on an upper surface of the sheet bundle at the first operating position, thereby applying the first pressing force to the sheet bundle on the basis of a resultant force of a gravitational force generated by its own weight and an biasing force generated by the compression spring, and the pressing block is pushed down by an expansion portion (61b) of the rod while the pressing block is kept being supported on the upper surface of the sheet bundle at the second operating position, thereby applying the second pressing force on the basis of a resultant force of the first pressing force and the push-down force generated by the rod.