A cylindrical lens array cannot be manufactured so that each cylindrical lens has the same radius of curvature and the same accuracy in the surface. Therefore, when the laser annealing is performed using the cylindrical lens array, the beam spots divided by the cylindrical lens array cannot be superposed completely in the same surface. As a result, there is a region where the energy is attenuated in the edge portion of the rectangular beam to be formed, and therefore the intensity distribution of the laser beam becomes inhomogeneous. In the present invention, the cylindrical lens array is used in combination with the optical waveguide. After dividing the laser beam in a predetermined direction by the cylindrical lens array, the divided beams are combined, and then the laser beam is incident into the optical waveguide that acts upon the same direction as the predetermined direction. This can correct the variation in the intensity of the laser beam due to the processing inaccuracy of the cylindrical lens array.