A substantially rectangular shadow mask is arranged opposite to a phosphor screen formed on an inner surface of a panel. The shadow mask has a mask body and a mask frame to which a peripheral portion of the mask body is attached. The shadow mask has a rectangular form having a center through which a tube axis passes, and a long axis and a short axis passing through the center and perpendicular to each other. The mask frame has a pair of long side walls extending parallel to the long axis and a pair of short side walls extending parallel to the short axis. The height of each long side wall at a central portion along the tube axis is lower than the height of each short side wall at a central portion along the tube axis.