Laser irradiation method and device

A plurality of parallel scanning lines are set in the x direction arranged with a scanning line gap Py in the y direction, the longitudinal direction of a linear laser spot (W) is oriented in the y direction, and laser light is irradiated on each irradiation position of width direction pitch [Lambda] while moving the laser spot (W) along the scanning line relative to an article to be processed. At that time, the irradiation position on adjacent scanning lines is offset by the position offset [delta]x in the x direction, and the scanning line gap Py, width direction pitch [Lambda], and position offset [delta]x are determined such that the cumulative value of the irradiated laser light intensity is substantially uniform. Thus, no difference appears in the amount of superimposition for a profile on an extension of the longitudinal axis Cy for irradiation position on odd-numbered scanning lines and the amount of superimposition for a profile on an extension of the intermediate axis My, and therefore, laser irradi