To simplify a device, and to facilitate maintenance by improving a cutting device disposing two to four rotary blades around a cut material so as to change position, and making these rotary blades simultaneously revolve along the outer periphery of the cut material.

In order to make a rotating surface plate itself have a simple structure having only a machine mechanism rotating the rotating surface plate on its axis, a structure wherein a rocking arm of the rotary blade is mounted on one surface of the rotating surface plate, and a driving motor and a rocking motor of the rotary blade of each rocking arm are individually mounted on the other surface for each rocking arm, is adopted. One side from the surface plate has only rotation cutting function, and disposal of cutting chips is extremely easily carried out. The other side is mounted with only rotating motor as a driving force, and cutting can be completed only by controlling the motor making the rotating surface plate itself rotate on its axis by a predetermined angle during cutting a round tube or a square tube with a square cross section.