A cathode ray tube is provided, in which the flatness of a tension mask constituting a color-selection mechanism is maintained by a suitable stretching force, while with the tension mask, the influence of external magnetic fields, such as the terrestrial magnetism is suppressed, and the shifting of the electron beam is reduced. A tension mask made of a magnetostrictive material is used, the tension mask is stretched by a stretching force in a range maintaining the flatness of the tension mask, and the direction and strength of the stretching force are set such that vertical magnetic permeability of the tension mask increases, due to a magnetoelastic effect caused by the stretching force in the magnetostrictive material of the tension mask.