To reduce the vertical elongation of a plate grating by forming an active-material-holding mesh-like part through expansion process by which a sheet strip is cut and expanded, and forming frame bones consisting of unexpanded parts at the top and bottom and the sides of the mesh-like part.

Frame bones 2, 3, etc., for a top and a bottom, etc., respectively, are formed at the top and bottom and sides of a net-like part serving as the active material holding part of an expanded (mesh-like) grating. Slits 5b each with a certain elevation angle 5c to the direction of a cold-rolled sheet strip 5 made of a lead alloy are cut in the sheet 5, and the slit groups each formed of an assembly of the slits are independent of one another for one grating, with an unexpanded part 5g left behind between the gratings that adjoin at a pitch 5a. By adjusting the pitch of the gratings, the interval 5d between the slits, the length 5e of the slit, the overlap length 5f of the adjacent slits, the elevation angle of the slit, and the like, the size of the mesh-like part of the grating after expansion and the length and width of the grating or the like can be freely designed for fabrication.