A flat color CRT wherein a single beam emitted from an electron gun scans the inner surface of a tube wall and which includes a phosphor screen formed on the walls inner surface. The phosphor screen comprises a nonluminescent substance and phosphor index stripes with the substance interposed between the stripes. Red, green, blue primary phosphor color stripes have a sufficient thickness and are arranged repeatedly on the nonluminescent substance at a spacing in a definite relation to the phosphor index stripes.