In a color cathode ray tube with a shadow mask shaped as a nonspherical surface, a structure in which the curved surface shape of the effective area of the shadow mask in which apertures through which electron beams pass to a fluorescent screen are formed is made such that, going along the X axis, minimal values of radius of curvature of lines of intersection of the shadow mask and Y-Z parallel planes parallel to the minor axis Y and a central axis which passes through the mask's center and is normal to the mask exist between the center and the edges of the effective area. This prevents local doming.