To provide a forming apparatus, which forms a plurality of through holes with desirable shapes on a thin metal sheet into a net-like state by effectively preventing undesirable deformation after the forming.

A metal lath forming apparatus R comprises: feed rollers OR for successively sending and supplying a thin metal sheet Z by a predetermined working pitch; and a blade die H for successively shearing the thin metal sheet Z supplied and forming net-like through holes into a zigzag pattern by stretching. The blade die H is composed of a lower die with a lower blade SH and an upper die with an upper blade UH. The lower blade SH is formed into such a curved shape that the supporting surface for the thin metal sheet Z is downward convex. The upper blade UH is composed of such a row of blades that a plurality of blades formed into nearly triangle shapes are arranged in series. Thereby, the stretching quantity of the thin metal sheet Z is made variable in the sheet width direction, so that warpage accompanying the generation of springback is hardly caused.