A processing method for a plate-shaped workpiece that has a transparent substrate, a first resin layer stacked on a front surface of the substrate, and a second resin layer stacked on a back surface of the substrate and in which the first resin layer is segmented into plural regions by plural planned dividing lines that intersect each other, includes sticking an expandable adhesive tape to the second resin layer, irradiating the workpiece with a laser beam with such a wavelength as to be absorbed by the first resin layer and transmitted through the transparent substrate, the laser beam removing the first resin layer along the planned dividing lines by ablation, the laser beam also forming a modified layer whose refractive index or mechanical strength is different from surroundings along the planned dividing lines.