A laser irradiation apparatus and a method of laser irradiation which can improve use efficiency of a laser beam, eliminate an influence of stray light at a DMD, and form an irradiation pattern with a homogeneous beam spot are provided. The laser irradiation apparatus includes at least a laser oscillator, a diffractive optical element, and an optical element having many minute mirrors arranged two-dimensionally. A laser beam emitted from the laser oscillator is divided into plural laser beams by a diffractive optical element and the laser beams are deflected by plural micromirrors. The divided laser beams have equal energy to each other.