A method of crystallizing an amorphous semiconductor film, the method comprising the steps of: forming a gate electrode on a transparent insulating substrate; forming a gate insulating film on the transparent insulating substrate and on an upper part of the gate electrode; forming an amorphous semiconductor film on the gate insulating film; forming a light-transmissive insulating film on the amorphous semiconductor film; forming a metal film having an opening on the light-transmissive insulating film; irradiating laser light onto both a region of the light-transmissive insulating film exposed by the opening and the metal film, which is used as a mask for shielding the laser light; and performing laser annealing to make the laser light to be absorbed through the light-transmissive insulating film into a region of the amorphous semiconductor film exposed by the opening, so that the amorphous semiconductor film is heated and converted to a crystalline semiconductor film.