In an exposure step for forming a phosphor screen of a color cathode ray tube, correction lenses which are arranged between a light source and a panel are used in a state that a common correction lens which is used in common for three colors and three kinds of monochroic correction lenses are combined. The present invention can, in a flat-face-type color cathode ray tube, prevent the generation of the mislanding attributed to the difference in a wall thickness between a center portion and a peripheral portion of a panel thus improving the color purity.