A shadow mask for a Cathode Ray Tube (CRT) which achieves a high brightness and white uniformity by minimizing light emission of incorrect colors, includes: an effective screen portion with a plurality of beam passage holes arranged in a predetermined pattern and a non-holed portion surrounding the effective screen portion with no beam passage holes. The beam passage holes have a large-sized hole portion on a side facing a panel of the CRT and a small-sized hole portion that is smaller than the large-sized hole portion on a side facing an electron gun are selected such. A concave portion is formed on each of the beam passage holes arranged in a direction from a center of the effective screen portion to a direction of emission, and the concave portion is varied from the center of the effective screen portion diagonally such that a serif width D satisfies D=a-bx+cx2 (wherein a, b, and c are constants, and x is a spatial distance from the center of the effective screen portion to the center of the beam passage hole) and a, b, and c are selected such that {c/(b+c has an absolute value between 0.0092 and 0.0099.