Die-cutting blade and case-forming die-cut blank

A sheet die-cutting blade comprising a strip-plate-shaped blade plate having a predetermined length and made of a steel plate having a thickness, the blade plate being provided with a pair of chamfers formed on the respective side surfaces of the blade plate so as to extend from one side edge of the blade plate at substantially the same inclination angle, the chamfers defining a cutting edge along the one side edge of the blade plate,

• wherein, when viewed in plan view in a direction perpendicular to the cutting edge and parallel to the blade plate, the cutting edge has a composite wave pattern comprising a large wave pattern undulating in a thickness direction of the blade plate and a small wave pattern undulating in the thickness direction of the blade plate, the large wave pattern comprising a plurality of longitudinally continuous large waves, the small wave pattern comprising a plurality of longitudinally continuous smoothly curved small waves, wherein each of the large waves contains a plurality of the small waves, and wherein the small wave pattern is entirely located within the thickness of the blade plate, wherein the wave widths W1 in the small wave pattern fall within a range of W1=0.02 mm to 0.5 mm.