When the power density of the incident laser beam exceeds a certain value, the interior of the material begins to evaporate at the point where the beam irradiates, forming holes. Once the incident light beam is formed, it absorbs all the energy as a black body. The hole is surrounded by a wall of molten metal, and then the auxiliary air flow coaxial with the beam carries away the molten material around the hole. As the workpiece moves, the small hole moves horizontally in accordance with the cutting direction to form a cutting seam. The laser beam continues to irradiate the front edge of the slit, and the molten material is blown away continuously or Pulsatively from the slit.