An oxygen-containing gas flow field is formed on a surface of a cathode side metal separator of a fuel cell. The oxygen-containing gas flow field is connected between an oxygen-containing gas supply passage and an oxygen-containing gas discharge passage. A coolant flow field is formed on the other surface of the cathode side metal separator, on the back of the oxygen-containing gas flow field. The cathode side metal separator has linear guide ridges protruding from an intermediate height area toward the oxygen-containing gas flow field to form a continuous guide flow field, and bosses protruding from the intermediate height area toward the coolant flow field to form an embossed flow field.