Provided is an organic EL display device capable of preventing or restraining color shift or color mixing in an image displayed in each of its pixels, this inconvenience being caused by the entry of light into the pixel from an organic EL element of a pixel adjacent to the pixel; and provided is a color filter forming substrate making it possible to produce such an organic EL display device. The color filter forming substrate is a substrate for an organic EL display device, in which: a pixel-dividing light-shielding region is arranged over one surface of a base material comprising a transparent substrate to make plural pixel regions into a region-divided form; and plural color-filter-forming coloring layers for multiple colors are arranged to the predetermined pixel regions in accordance with the respective colors, characterized in that a light-shielding layer is arranged in the pixel-dividing light-shielding region, and a surface of the light-shielding layer farthest from the one surface of the base material is positioned farther from the one surface of the base material than respective surfaces of the color-filter-forming coloring layers in the respective colors, these surfaces not being respective base material side surfaces of the coloring layers, are positioned.