A stretched mask having a high tensile strength and favorable high-temperature creep properties and free from tape twist, and a material for the stretched mask. A low-carbon steel sheet containing 70 ppm to 170 ppm of nitrogen on a weight basis is heat-treated at a temperature at which recrystallization does not take place. The heat-treated material is provided with a resist pattern for forming apertures and subjected to etching to form apertures.