PURPOSE: To straighten easily a residual distortion, and to obtain an uneven pattern which is beautiful and abounds in cubic feeling, by heating a metallic thin sheet to a specified temperature, and executing in order an embossment and a straightening of the residual distortion under a tension.

CONSTITUTION: A coil A installed to an uncoiler 1 is drawn by the first pinch roller 2, and fed to a loop part 3. Subsequently, the coil A is guided by a pinch roller 4, fed to a heater 5, heated to about 30W60°C, its face film is softened to a prescribed hardness, and it is fed to an embossing roll 7. In this roll, an embossing pattern consisting of a recessed part and a projecting part is formed continuously on the coil A. The coil A discharged from the embossing roll 7 is straightened by a leveler 8 in a state that the residual distortion at the time of embossing is drawn by the fourth pinch roller 9, and fed to the next process.