A shadow mask includes a mask substrate having vertical and horizontal axes passing through a center of the substrate, and a number of substantially rectangular apertures. The apertures are arranged so that a plurality of vertical trains of apertures extending parallel to the vertical axis are arranged at predetermined intervals in the direction of the horizontal axis. Each of the apertures other than the apertures located on the vertical axis has a pair of outer corners distant from the vertical axis, a pair of inner corners less distant from the vertical-axis side, and a pair of bulging portions extending from the outer corners, respectively, outward in the horizontal direction. The farther each of the apertures is located from the vertical axis, the longer the bulging portions extend outward.