PURPOSE: To make it possible to form a microscopic contact hole with a high degree of reproducibility without giving a substantial effect on the wiring of the under layer by a method wherein, after an auxiliary laser beam has been projected on the required part on a substrate for the period, or longer, in which the average heat diffusion distance of a thin film becomes longer than the thickness of the thin film, a pulse laser beam is projected.

CONSTITUTION: Before the pulse laser beam emitted from a pulse laser beam source 1, with which a thin film will be removed, is made to irradiate when a transparent thin film, located on a substrate having an absorbing layer under the transparent thin film, a continuous laser beam or an auxiliary laser beam having a long pulse width, emitted by an auxiliary laser beam source 2, is made to irradiate on the part desired to be processed in advance. The irradiation period of the laser beam is set in such a manner that the average heat diffusing distance, which is determined by the irradiation period and the heat diffusivity, becomes longer than the thickness of the thin film in order to add thermal distortion on the whole thickness direction of the thin film which is desired to be removed. As a result, the required processed shape can be formed in an excellent reproducible manner without giving a substantial effect on the wiring layer of the under layer.