A polymer electrolyte fuel cell includes an electric power generating cell provided with a fuel electrode, an oxidizer electrode, a polymer electrolyte membrane sandwiched between the fuel electrode and the oxidizer electrode and a separator formed with a gas flow passage for reaction gas to be supplied to at least one of the fuel electrode and the oxidizer electrode. Also, the polymer electrolyte fuel cell includes a flow passage changeover mechanism changing over a configuration of the gas flow passage in accordance with an operating condition of a polymer electrolyte fuel cell.