Abstract: An apparatus for cutting a sheet stack is provided. The sheet stack is composed of a plurality of sheets. The apparatus includes a cutting blade having a plate form and having a cutting edge at one side extending along a cutting width direction. The cutting blade has at the one side: a plurality of projecting blade portions having ridge lines forming edge lines capable of thrusting and sawing cutting, the projecting blade portions projecting in a cutting direction; and a straight bottom portion between adjacent projecting blade portions. Cutting of the sheet stack is performed by applying a load to the cutting blade in the cutting direction, and by reciprocating the cutting blade along the cutting width direction.