PURPOSE: To reduce the attachment of dross in cutting by a laser beam a material with a high caking property, which is a fused object of a stainless steel billet, a galvanized billet, an aluminum plate, etc.

CONSTITUTION: A work nozzle 80 with an opening part 10 with a major axis and a minor axis, is used, and a material is cut at a state in which the major axis direction always parallels a cutting direction. Consequently, in cutting by a laser beam a material with a high caking property, which is a fused object of a stainless steel billet, a galvanized billet, an aluminum plate, etc., there is an effect which the material can be cut by a laser beam, with extremely less attachment of dross to the material.