The present invention provides a metal separator for a fuel cell, which is formed by stamping molding a first metal thin plate and a second metal thin plate, the metal separator comprising: at least one cooling flow field enclosed by inner surfaces of the first and second metal thin plates; first and second main flow fields enclosed by outer surfaces of the first and second thin plates, respectively; and first and second auxiliary flow fields formed on a top surface of the first main flow field and a bottom surface of the second main flow field, respectively.