PURPOSE: To form a perforated metal plate effectively without any waste by working the stretched metal plate in a plane shape with its pressing or rolling with a roll after stretching the metal plate after cutting a cut or making a small hole thereon.

CONSTITUTION: In the case of manufacturing the perforated metal plate used for the case material of an electric apparatus, etc. a cut 2 is first cut or a small hole 3 is made on a metal plate 1. The cut metal plate is then stretched in the direction about at right angles with the cut and the perforated metal plate is stretched in an optional direction. The stretched metal plate is thereafter worked in a plane shape with its pressing or roll-rolling. Since the hole area is thus increased by the stretching of after cutting or making small holes the reduction in the material yield can be eliminated and the cost of a product can be reduced.