Fuel cells, fuel cell system and a fuel cell module and fuel cell device

A fuel cell capable of suppressing deformation during reduction treatment, the cell stack apparatus using the same, to provide a fuel cell module and a fuel cell device. A Fuel cell of the present invention, the fuel electrode layer 4 provided on the solid electrolyte layer 3, On the fuel electrode layer 4, it is provided adjustment layer 9 that expands by the interconnector 6 and a reducing atmosphere to shrink at adjusting layer 9 or a reducing atmosphere to shrink at the interconnector 6 and the reducing atmosphere expands in a reducing atmosphere since the, possible to provide a fuel cell 1 that suppresses deformation in the reduction process. .FIELD 1