PURPOSE: To cut a traveling band-like material into a plurality of piece materials and efficiently cut off a corners of each piece material by providing a corner cutting blade in at least one of a pair of blades comprising a fixed blade and a rotary blade at a position corresponding to a corner of each piece material to be separated from the band-like material.

CONSTITUTION: With a rotary blade 34 made to slide contact with a fixed blade 32 at a fixed cycle, a continuously supplied band-like material (such as continued bag body) is cut into a plurality of piece material (such as bag bodies) 54 at a fixed interval by the cooperative work of the fixed blade 32 and rotary blade 34. At the same time, a corner of each piece material is sheared off by a plurality of corner cutting blades 40 arranged in middle sections in a linear blade section of the rotary blade 34.