NOVELTY - A metal gas diffusion layer is formed by using a forming apparatus having a stationary die on which a metal sheet is placed, and a cutting die which is biased from the stationary die in a direction of feed of the metal sheet and which advances and retreats in a thickness direction of the metal sheet and moves in a width direction of the metal sheet to cut the metal sheet for forming through holes.    USE - For forming a metal gas diffusion layer for a fuel cell, e.g. polymer electrolyte fuel cell.    ADVANTAGE - The method lowers pressure loss with supply of gas to efficiently and smoothly supply gas, and the fuel cell attains compatibility between good efficiency in generation of electricity and reduction in size.    DETAILED DESCRIPTION - Metal gas diffusion layer formation where through holes are arranged in a staggered fashion for supplying a fuel gas or an oxidizer gas in a diffused condition to an electrode layer of an electrode of a fuel cell involves:    (1) using a forming apparatus having a stationary die on which a metal sheet is placed, and a cutting die which is biased from the stationary die in a direction of feed of the metal sheet and which advances and retreats in a thickness direction of the metal sheet and moves in a width direction of the metal sheet so as to cut the metal sheet for forming through holes each having a desired shape and, arranged in a staggered fashion; executing machining cycle of feeding the metal sheet by a machining pitch and advancing and retreating the cutting die in the thickness direction of the metal sheet to form the through holes; and    (2) moving the cutting die in the width direction of the metal sheet by a predetermined distance and executing the machining cycle and moving the cutting die by the predetermined distance in a direction opposite that of the moving of the cutting die along the width direction of the metal sheet.    DESCRIPTION OF DRAWING(S) - The figure is a view of a metal lath used to form the collector.