PURPOSE: To enable one person to use simultaneously 4W5 units of a titled machine and to improve the efficiency of cutting by discriminating the line marked off on a web surface and executing continuously cutting of only the assigned drain hole unattendedly.

CONSTITUTION: The prescribed mark is marked off in, for example, the drain hole opening position of a shape steel 100 which is a blank material. The operator sets a carriage 1 to the optional position at the end of the steel 100 and starts the carrier to run. The optical sensor 4 of the carriage 1 detects the marking in the hole opening position and outputs a control signal to a control device 3 which stops first the run f the carriage 1. A hole cutter 2 is then operated to start cutting after the start position for cutting is pierced. The operation of the cutter 2 is stopped when the cutter is reset to the pierced position after the cutting to the prescribed hole shape is ended. The carriage 1 is again run to search for the succeeding marking position.