Method for producing solid electrolyte structure with porous portion and dense portion

A first fine particle-containing solution is deposited on an appropriate substrate, and dried to form a first fine particle aggregate layer. Polymer particles are deposited on the first fine particle aggregate layer, and are supplied with a second fine particle-containing solution such that the polymer particles are immersed in the second fine particle-containing solution. The second fine particle-containing solution is dried to form a second fine particle aggregate layer containing a large number of the polymer particles embedded. A first structure precursor is completed at this stage. Then, the first structure precursor is separated from the substrate, and thermally treated. Thus, the production of a first solid electrolyte structure, which has a porous solid electrolyte portion and a dense solid electrolyte portion integrated, is completed.