PURPOSE: To correct a cutting length without stopping a cutting cycle by setting a correction value of the cutting length and adding the correction value of the cutting length to a preset cutting length at the completion of each cutting cycle.

CONSTITUTION: A correction value memory part 25 reads a correction no. Tn from a correction no. memory part 24 and sends a correction value Cn to an adder 26. The adder 26 adds the correction value Cn to a cutting length L from a cutting length memory part 22 and sends it to a converter 27. An adder 13 adds the number of pulses of corrected cutting length from the adder 27 to the value PCOUNT on a pulse counter stored in the previous cutting cycle in a cutting start counter memory part 17. The pulse counter 12 reads pulses PS from a pulse generator 5, set them as FEEDC, sends them to a comparator 14, compares them with the values from the adder 13 and, when the values become FEEC≥PCOUNT+Lp, opens a gate G3, and sends them to the cutting start counter memory part 17 through a gate 4.