Disclosed is a flat type color cathode ray tube of high quality, which is capable of maintaining a brightness and brightness uniformity of an image while improving contrast, thereby ensuring flatness and visual distinction of the image. The flat type color cathode ray tube comprises a panel having an outer surface which is substantially flat and an inner surface which takes a predetermined curvature. The panel possesses at a center part thereof a transmittance of 45%˜75%, and the inner surface of the panel possesses an on-diagonal-axis curvature RD which satisfies a correlation, 3.5R≦RD≦8.0R where R is a product of 1.767 and a diagonal length of an effective surface along a diagonal axis.