Provided are a method of heating a composition which is applicable to a substrate provided with a material having low heat resistance and a method of forming a glass pattern which leads to reduction of cracks. A composition formed over a substrate is irradiated with a laser beam to bake the paste through local heating. Scan with the laser beam is performed so that there can be no difference in the laser beam irradiation period between the middle portion and the perimeter portion of the composition. Specifically, irradiation with the laser beam is performed so that the width of the beam spot overlapping with the composition in the scanning direction is substantially uniform.