An amorphous silicon film on an insulating substrate portion to be formed as an individual display panel in a large-sized insulating substrate is irradiated with a continuous-wave (CW) solid-state laser beam condensed linearly, while being scanned therewith at a fixed speed in the width direction of the condensed laser beam. A pixel portion and a peripheral circuit portion in the same insulating substrate portion are irradiated with the laser beam temporally modulated to have a power density high enough to provide predetermined crystallinity. The amorphous silicon film is transformed into a silicon film having crystallinity corresponding to performance required for thin film transistors to be built in each of the pixel portion and the peripheral circuit portion. In such a manner, a thin film transistor circuit having optimum crystallinity required in the pixel or peripheral circuit portion can be obtained while high throughput is kept. Thus, a product having good display features as a display panel can be provided inexpensively.