The ???liquid state (fluid state)??? denotes a concept including a paste state as long as the material can be supplied onto the surface of the solid electrolyte layer 13 and is a state where the material has viscosity in a range from about 100 cP to 1,000,000 cP. In particular, the cathode 14 has, for example, as shown in FIG. 2, a two-layer structure in which the main electrode layer 14B is stack