To provide a method of manufacturing a solid ion conductor without needing a dopant, especially it is enhanced in oxygen conductivity.

This manufacturing method of solid ion conductor is characterized in that each solution of each metallic coordinate compound constituting the ion conductor of solid electrolyte is mixed in such a way that the amount of each metal constituting the final ion conductor of solid electrolyte is stoichiometric amount, then polymerizer is added thereto so as to polymerize the coordinate compound in the solution, the obtained polymer is dried, fired, and crushed, wherein the crushed matter is formed into film-plate state compact, the firing temperature is set at the point that the half width of the X-ray diffraction pattern at about 2θ =30° is in a range between 0.2-5°.