A color cathode ray tube in which an aperture grill is provided having a large number of slits extended in the extending direction of fluorescent stripes bored through the grill in parallel. The slits are provided in an opposing relation to a color fluorescent screen in which the fluorescent stripes of respective colors are arranged in a predetermined order in parallel. The aperture grill is composed of a thin plate having the slits. This a frame on which the thin plate is extended with a predetermined tension in the extending direction of the slits and this thin plate is formed of a high purity iron thin plate having a thickness of equal to or less than 0.05 mm. Since the thickness of the thin plate is selected as described above, controllability of the width of the slit in the manufacturing process can be improved. Therefore, the accuracy of the aperture grill can be increased, the productivity thereof can be increased, the weight thereof can be reduced, and further, the color cathode ray tube can be formed as a high definition color cathode ray tube.