It is an object of the present invention to provide a laser irradiation apparatus and a laser irradiation method for conducting a laser process homogeneously to the whole surface of a semiconductor film. A first laser beam emitted from a first laser oscillator passes through a slit and a condensing lens and then enters an irradiation surface. At the same time, a second laser beam emitted from a second laser oscillator is delivered so as to overlap the first laser beam on the irradiation surface. Further, the laser beams are scanned relative to the irradiation surface to anneal the irradiation surface homogeneously.