A separator for a fuel cell comprises a corrugated or undulated gas flow path portion (4) formed on central portion (2) of a clad thin plate: and a flat portion (6) formed on an outer periphery of the central portion, wherein the clad thin plate is obtained by applying rolling work on a metal plate whose surface is covered with a precious metal layer at a draft of 5% to 15% to make clad, and a limit plate thickness residual rate indicating a boundary limit in which cracking of the precious metal layer in the clad thin plate and reduction of corrosion resistance due to exposure of the metal plate are negligible is obtained in advance, wherein regarding a sectional shape in a direction orthogonal to a flow path of the gas flow path portion (4), when a plate thickness of the thinnest portion of a rib shoulder portion is represented as t2 and a plate thickness of a peripheral portion of the separator is represented as t4, a relationship of t2≧t4×limit plate thickness residual rate is satisfied.