To improve work efficiency in a series of cutting of short material by providing a magnet and a magnet operating device performing work of rotating the short-sized material by about 90°.

After cutting a first cut part in short material W, in the state of attracting a center-of-gravity part of the short maternal W by a magnet 59, the magnet 59 is rotated by about 90 integrally with a rotating member 77 of a magnet operating device 61 by the operation of the rotating member 77. The short-sized material W is thereby rotated integrally by about 90° so as to place a second cut part in the short material W almost parallel in an X-axis direction, and the second cut part in the short material W is cut in a cutting position by a band saw blade 5 in a traveling driven state.