An object of the present invention is to provide a laser irradiation method and a laser irradiation apparatus for irradiating an irradiation surface with a linear beam having more homogeneous intensity by blocking a low-intensity part of the linear beam without forming the fringes due to the diffraction on the irradiation surface. In the laser irradiation, a laser beam emitted from a laser oscillator 101 passes through a slit 102 so as to block a low-intensity part of the laser beam, the traveling direction of the laser beam is bent by a mirror 103, and an image formed at the slit is projected to an irradiation surface 106 by a convex cylindrical lens 104.