To provide a manufacturing method of a porous metal foil sheet easy to work, capable of reducing working cost and preventing production of burrs and breakage when worked, and having strength.

This forming method is to laminate an ultraviolet ray hardening type, heat peeling type or water soluble adhesive tape 2 on a metal foil sheet 1 of less than 50 μm thick, to uniformly drill a large number of holes 5 numerical aperture of which is to be more than 25% by punching work on the ultraviolet ray hardening type adhesive tape 2 and the metal foil sheet 1, to lose adhesive force from the adhesive tape 2 and to peel the adhesive tape 2 from the metal foil sheet 1.