The present invention provides a laser irradiation apparatus which can accurately control positions of beam spots of laser beams emitted from laser oscillators and the distance between the adjacent beam spots. A laser irradiation apparatus of the present invention includes a first movable stage with an irradiation body provided, two or more laser oscillators emitting laser beams, a plurality of second movable stages with the laser oscillators and optical systems provided, and a means for detecting at least one alignment maker. The first stage and the second stages may move not only in one direction but also in a plurality of directions. Further, the optical systems are to shape the laser beams emitted from the laser oscillators into linear beams on the irradiation surface.