SOLID OXIDE FUEL CELL, CELL STACK DEVICE, FUEL CELL MODULE, AND FUEL CELL DEVICE

[Problem] To provide: a solid oxide fuel cell in which stress to be generated in a solid electrolyte layer can be suppressed; a cell stack device; a fuel cell module; and a fuel cell device. [Solution] A solid oxide fuel cell which is characterized in that: a fuel electrode layer (3) is arranged on one main surface of a solid electrolyte layer (4) that has gas blocking properties, and an oxygen electrode layer (6) is arranged on the other main surface of the solid electrolyte layer (4); the solid electrolyte layer (4) has a thickness of 40 µm or less; the solid electrolyte layer (4) has a porosity of 3-15% by area in an arbitrary cross-section; and pores (B) in the solid electrolyte layer (4) have an average pore diameter of 2 µm or less.