A cell structure includes a cathode, an anode, and a solid electrolyte layer interposed between the cathode and the anode, the cathode being in the form of a sheet, the anode being in the form of a sheet, the solid electrolyte layer being in the form of a sheet, the solid electrolyte layer being disposed on the anode, the cathode being disposed on the solid electrolyte layer, the cathode having a resistance Rc, the anode and the solid electrolyte layer having a resistance Ra, the resistance Rc and the resistance Ra satisfying a relationship of Rc/Ra≥0.3, the cathode including a first metal oxide having a perovskite crystal structure, the cathode having a thickness larger than 15 μm and equal to or less than 30 μm.