PURPOSE: To shorten a time for swing motion as well as to attempt an improvement of cutting capacity for cutting a trapezoidal form by controlling the speed in the horizontal direction of a swing table to coincide with the speed of a plate.

CONSTITUTION: A plate to be cut out is inserted between an upper cutting blade 27 and a lower cutting blade 38 by way of a guide table. A control is so assumed that the speed in the horizontal direction of a swing plate 31 coincides with the speed of the plate at the time when the upper cutting blade 27 falls upon the lower cutting blade 38 whereby the plate is cut out. A control of the angle of tool rests 22 and 37 in order to cut the plate into a trapezoidal form, has been electrically set before the cutting is started. After the cutting is performed in this state, the tool rest 22 is reset to a required angle for performing the cutting. Operations as described above are repeated for cutting the plate into a trapezoidal form.