NOVELTY - The separator (100) has a carbon thin film (120) formed on an electrically-conductive metal base substrate (110) and including a first layer (121) formed closest to the metal base substrate. A second layer (122) of the thin film is formed farthest from the substrate. Diameter of carbon particles included in the first layer is 19 nm, and is smaller than diameter of carbon particles included in the second layer of the thin film. The diameter of the carbon particles included in the second layer is 40 nm. An intermediate layer (112) is provided between the substrate and the film.    USE - Fuel cell separator for a fuel cell (claimed) i.e. polymer electrolyte fuel cell, in a vehicle.    ADVANTAGE - The carbon thin film contained with minute carbon particles is formed on the base substrate so as to improve corrosion resistance effect and conductivity of the separator. The separator is simple to manufacture, and has low production cost, high usability, better gas barrier property and electronic conductivity, and saves resources consumption. The diameter of the carbon particles included in the first layer is 19 nm or less so as to improve adherence between the base substrate and the first layer of the carbon film by the intermediate layer, thus restraining the base substrate from corroding due to water including corrosive substances, and hence restraining durability output of a fuel cell. The diameter of the carbon particles included in the second layer is 40 nm or less so as to improve deposition rate and production efficiency of the separator. The separator ensures that an electrolyte membrane is a polymer electrolyte membrane to be made of fluorine-based sulfonic acid polymer as solid polymeric material, so that the electrolyte membrane provides better proton conductivity under wet condition.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a fuel cell    (2) a method for manufacturing a fuel cell separator.    DESCRIPTION OF DRAWING(S) - The drawing shows an enlarged sectional view of a section of a separator.    Fuel cell separator (100)    Electrically-conductive metal base substrate (110)    Intermediate layer (112)    Carbon thin film (120)    Layers of the carbon thin film (121, 122)