A substrate mark is formed on a transparent substrate as an alignment mark. The substrate mark is formed at the same time as transparent electrodes are formed on the transparent substrate. The substrate mark is formed of the same material as the transparent electrodes. A center wavelength of a transmission wavelength of a plurality of optical filters is different from each other. An optical filter corresponding to a thickness of the substrate mark is selected from a plurality of optical filters. Light is irradiated from a white light source to the substrate mark via the selected optical filter. Accordingly, the substrate mark is recognized and a shadow mask is aligned with the transparent substrate.