A solid oxide fuel cell for generating electricity by reacting hydrogen and oxidant gas in a fuel cell unit, the fuel cell unit comprises: a fuel electrode to which hydrogen is supplied, wherein the fuel electrode comprises a composite material containing nickel and shrinks by oxidation in the temperature range between 350° and 400° Celsius; an oxidant gas electrode to which oxidant gas is supplied; and a solid electrolyte placed between the fuel electrode and the oxidant gas electrode; and a reaction prevention layer placed between the fuel electrode and solid electrolyte to prevent a chemical reaction between the fuel electrode material and the solid electrolyte material; wherein the fuel cell unit contains a fuel gas flowpath for directing fuel gas containing hydrogen; and the fuel cell unit has an electrical generation laminated section in which the fuel electrode, the reaction prevention layer, the solid electrolyte and the oxidant gas electrode are laminated in that order starting from the fuel gas flowpath side;; wherein the solid oxide fuel cell has: a fuel cell module comprising the aforementioned fuel cell unit; a fuel supply apparatus for supplying fuel to the fuel cell module; a water supply apparatus for supplying steam reforming water to the fuel cell module; an oxidant gas supply apparatus for supplying oxidant gas to the oxidant gas electrode of the fuel cell unit; a reformer disposed inside the fuel cell module, for steam reforming fuel supplied from the fuel supply apparatus using water supplied from the water supply apparatus; a fuel/exhaust gas passage (21 b) for directing fuel/exhaust gas to outside the fuel cell module from the fuel supply apparatus through the reformer and the fuel cell unit fuel gas flowpath; and a controller for controlling the fuel supply apparatus, the water supply apparatus, the oxidant gas supply apparatus, and the extraction of power from the fuel cell module; wherein the controller is equipped with a shutdown circuit for stopping the supply of fuel and electrical generation, the fuel/exhaust gas passage (21 b) is configured to function as a mechanical pressure retaining means for maintaining pressure inside the fuel gas flowpath of the fuel cell units at a higher level than the pressure outside the fuel cell units in the fuel cell module until the temperature of the fuel electrodes declines to 400°C after the supply of fuel and generation of electricity is stopped by the shutdown circuit; and the shutdown circuit has a pressure maintaining control circuit for executing a pressure retaining control to increase pressure inside the fuel gas flowpath in order to maintain the entire surface of the fuel gas flowpath side of the fuel electrode forming the electrical generation laminated section in an oxy-gen-free atmosphere by suppressing pressure drops in the fuel gas flowpath caused by temperature drops in the fuel electrode down to 350°C after the fuel electrode temperature declines to 400°C. a fuel electrode to which hydrogen is supplied, wherein the fuel electrode comprises a composite material containing nickel and shrinks by oxidation in the temperature range between 350° and 400° Celsius; an oxidant gas electrode to which oxidant gas is supplied; and a solid electrolyte placed between the fuel electrode and the oxidant gas electrode; and a reaction prevention layer placed between the fuel electrode and solid electrolyte to prevent a chemical reaction between the fuel electrode material and the solid electrolyte material; a fuel cell module comprising the aforementioned fuel cell unit; a fuel supply apparatus for supplying fuel to the fuel cell module; a water supply apparatus for supplying steam reforming water to the fuel cell module; an oxidant gas supply apparatus for supplying oxidant gas to the oxidant gas electrode of the fuel cell unit; a reformer disposed inside the fuel cell module, for steam reforming fuel supplied from the fuel supply apparatus using water supplied from the water supply apparatus; a fuel/exhaust gas passage (21 b) for directing fuel/exhaust gas to outside the fuel cell module from the fuel supply apparatus through the reformer and the fuel cell unit fuel gas flowpath; and a controller for controlling the fuel supply apparatus, the water supply apparatus, the oxidant gas supply apparatus, and the extraction of power from the fuel cell module;