The present invention provides an image display device capable of displaying a good image by suppressing yellowing of a glass substrate, and a high-yield manufacturing method of the glass substrate. The image display device is formed of a front-side glass substrate and a back-side glass substrate. In this manufacturing method, a glass substrate is used as the front-side glass substrate when Sn.sup.++ content in the glass substrate is a predetermined value or less, and the glass substrate is used as the back-side glass substrate when the Sn.sup.++ content exceeds the predetermined value.