To simplify a cell structure of an Na/X secondary battery, simplify a process of manufacture, improve productivity, so that a cost reducing effect of a cell can be expected, also simplify a module structure, make protection capable even without forming an excessive pressure resisting double structure.

A fused salt is used, a plurality of solid electrolytes making an Na ion pass through are aggregated, a module 12 is constituted. Here, a surface of each solid electrolyte tube 28 of the module 12 is surrounded by a fine hole substance 23 as wetted sufficiently by liquid sodium, a protection tube 24 protecting the solid electrolyte tube 28 is provided in the outside, so as to open a lower part of the protection tube 24 in the liquid sodium 14 also store the module 12 of solid electrolyte in a cylindrical pressure resisting vessel 13 consisting of pressure resisting and heat resisting material storing fused salt or the liquid sodium 14.