NOVELTY - The metal separator (10) has concave portion (21) for forming gas passage way, formed at main surface of side laminated by solid-polymer electrolyte film of metal-plate material, by press stamping. Metal plate material has main portion (13) having specific chemical composition, and metal coated portion (12). Ratio of board thickness (t) of main portion and average grain size (d) observed in plate surface of main portion, is 0.1-0.4.    USE - For fuel cell (claimed) such as polymer electrolyte fuel cell, phosphoric acid form fuel cell, solid electrolytic form fuel cell and molten carbonate form fuel cell used for electric vehicle.    ADVANTAGE - The metal separator has excellent workability, and effectively prevents corrosion of main portion.    DETAILED DESCRIPTION - The metal separator (10) has a concave portion (21) for forming gas passage way, formed at main surface of a side laminated by a solid-polymer electrolyte film of a metal-plate material, by press stamping. The metal plate material has a main portion (13) and a metal coated portion (12) covering the surface of main portion. The main portion contains (in mass%) nickel (Ni) (30-82), chromium (Cr) (15-30), molybdenum (Mo) (2-4), copper (Cu) (1-4), titanium (Ti) (0.1-3), iron and impurity (51.9 or less). The sum total content of the components (Ni, Cr, Mo, Cu and Ti) is 48.1 mass% or more. The metal coated portion has thickness of 1-500 nm and contains noble metals. The ratio of board thickness (t) of the main portion, which is 0.01-0.3 mm, and the average grain size (d) observed in the plate surface of the main portion, is 0.1-0.4. Both the surfaces of the solid polymer electrolyte film are covered with electrode layer. The main portion further contains carbon and sulfur, and the metal coated portion comprises gold, silver, platinum, ruthenium and palladium.    DESCRIPTION OF DRAWING(S) - The figure shows a partial cross sectional view of a separator.    separator (10)    metal coated portion (12)    main portion (13)    convex portion (20)    concave portion (21)