To improve processing accuracy and quality by restraining the generation and re-adhesion of a blow-off molten material.

In a forming processing of a hole or groove by a laser light, first, a surface of a workpiece 6 and its proximity surface layer portion are irradiated with a laser light B of the first energy, which is equal to or slightly larger than a given processing threshold. The deeper portion of the workpiece is irradiated with the laser light of the second energy, which is substantially larger than the first energy, and processed. A given processing threshold is decided based on the required minimal irradiation energy for at least heating the workpiece to the melting point and starting the removal of the material. The laser light is preferably a Q switch oscillation YAG laser which has a short pulse width and less thermal effect. The irradiation energy is controlled by adjusting the peak output, power density, pulse width, or the irradiation number and the like. This makes it possible to process a fine and deep hole or groove which has less contamination and good shape with respect to various materials.