Provided is an electronic device having a long life and a large effective area. Furthermore, provided is an optical device capable of controlling specular visibility. And provided is a substrate for the optical device, which includes a scattering layer having excellent scattering properties and having a desired refractive index while retaining surface smoothness. Further, there is provided a substrate for the electronic device, which includes a substrate having first and second main surfaces facing each other and an electrode pattern formed on the first main surface of the substrate, in which the first main surface of the first and second main surfaces is a surface which forms waviness made up of curved faces, the waviness of the surface has a wavelength Rλa of greater than 50 μm and a ratio Ra/Rλa of waviness roughness Ra of the surface which forms waviness to the wavelength Rλa of the waviness is from 1.0×10−4 to 3.0×10−2.