The purpose of the present invention is to provide a simple, compact fuel cell configured so as to have sufficiently large cell capacity and energy density. This fuel cell 10 has a cylindrical electrode assembly 12, an anode fuel substance body 14, a heater 16, and a sealed container 20. The electrode assembly 12 comprises a cylindrical, airtight solid electrolyte 12a, a cathode 12b, and an anode 12c. The solid electrolyte 12a conducts oxygen ions. The cathode 12b is formed on the inside surface of the solid electrolyte 12a, and reduces oxygen in air to oxygen ions during discharge. The anode 12c is formed on the outside surface of the solid electrolyte 12a, and oxidizes hydrogen gas to water vapor during discharge. The anode fuel substance body 14 reacts with water vapor to generate hydrogen gas, and becomes an oxide. The heater 16 is arranged on the outside of the sealed container 20 and/or the inside of the electrode composite 12. The sealed container 20 is arranged on the outside of the electrode assembly 12, sealing inside the electrode assembly 12 together with the anode fuel substance body 14.