An object is to provide a laser light irradiation apparatus and a laser light irradiation method which reduce errors of an irradiation position of laser light to an irradiated object and allow irradiation with laser light of any size when the irradiated object is irradiated with the laser light through a beam expander optical system. One feature of a laser light irradiation apparatus of the present invention is to include a laser oscillator; a beam expander optical system having a zoom function; and a correction lens disposed to conjugate the laser oscillator and the beam expander optical system including at least a first lens, a second lens, and a third lens in order in a traveling direction of the laser light, wherein the second lens and the third lens are cooperated with each other in accordance with the magnification of the laser light.