Provided are an image display device capable of displaying a good image by suppressing yellowing of a glass substrate, and an evaluating method of the glass substrate. The image display device is formed using the glass substrate where reflectance at wavelength of 220 nm is 5% or lower. In the evaluating method of the glass substrate for the image display device, Sn.sup.++ content in the glass substrate is analyzed using reflectance at wavelength of 220 nm.