PURPOSE: To reduce idle time and to improve product yield by cutting an extruded material at a predetermined position without stopping the extruding work during operation.

CONSTITUTION: An extruded material is cut by a cutter 5 while continuously extruding a billet 6 in a container 1 by a dummy block 2. Next, when the extrusion of billet 6 is finished, only a discard is treated without performing an initial cutting, and a new billet 6 is used to extrude a new extruding material 8 in succession to the rear end of a preceding extruded material 7. In a state of continuing the extruding work; when a stop mark 9 at the boundary between the materials 7, 8 arrives at the position of cutter 5, the materials 7, 8 is cut at the mark 9 without stopping the extruding work. Thereafter, the same operation is repeated for the next new billet, and a reject caused by the initial cutting is not produced.