Laser processing method and laser processing apparatus

A laser processing method using laser beam from a laser oscillator to emit continuously a light pulse having a large spacial and temporal energy concentration in a pulse emission of a period of one picosecond or less, and projecting a mask pattern with a projection lens onto a work piece almost transparent to the wavelength of said laser beam for sublimation processing thereof, comprising the steps of:

• setting the focal point of a projection image of said mask pattern on a surface of a contour boundary on the opposite side of said work piece irradiated by said laser when said processing begins, and irradiating and converging said laser beam on said focal point portion so as to make the energy concentration thereof to be more than a threshold value enabling designated ablative action to be generated;
• moving said work piece in the direction of laser irradiation gradually in a designated amount or at a designated speed in synchronism with the progress of ablation processing by the irradiation of said laser beam;
• and
• forming structure on said work piece in the form of being inserted into and drawn from the contour boundary surface on the opposite side of laser irradiation to the side of said laser irradiation,wherein when a structure is processed in the interior of the work piece by sublimation in performing the sublimation processing of said work piece, said structure is processed after a releasing outlet is formed in advance to release externally substance produced by sublimate evaporation of said processing.