A polymer electrolyte fuel cell of the present invention includes a membrane-electrode assembly (5) and separators (6A, 6B). A plurality of reactant gas channels are formed on a main surface of at least one of the separator (6A, 6B) and a gas diffusion layer (3A, 3B). In a case where among the plurality of reactant gas channels, a reactant gas channel overlapping the peripheral portion of the electrode (4A, 4B) twice is defined as a first reactant gas channel, and a reactant gas channel formed to overlap the peripheral portion of the electrode (4A, 4B) and formed such that the length of a portion overlapping the peripheral portion is longer than a predetermined length is defined as a second reactant gas channel, the second reactant gas channel is formed such that the flow rate of a reactant gas flowing therethrough is lower than that of the reactant gas flowing through the first reactant gas channel or the second reactant gas channel does not exist.