A color cathode ray tube comprising a perforated molded mask curved inward in the middle between its two opposite sides and having round corners, and a support frame curved outward in the middle between its two opposite sides and having round corners, wherein the corners of mask are respectively brought into contact with the corners of the mask and the frame. Therefore, the alignment accuracy between a shadow mask assembly and phosphor film and the magnetic shielding of the color cathode ray tube can be improved.