To eliminate trouble of the deformation of a shield member for liquid- storing due to changes with time by a method wherein the shield member, which solves such a problem that strong acid electrolytic water is affected by light, heat, etc., to be gradually decomposed, is formed of an on-liquid- floatable type plate-like or sheet-like body having a polygonal face.

A liquid-storing shield member comprises a plate-like body, or a sheet-like body, having a hexagonal face, and blocks a liquid stored in a liquid-storing container from air, etc. The material for this shield member is preferably a material having properties of floating on water, such as wood, in the case where the liquid is, for example, water. Further, in the case where the shield member has a hollow structure, a synthetic resin or metal such as steel, aluminum and stainless steel can also be used as the material for the shield member. As such a liquid-storing shield member, a plurality of shield members are used in the liquid-storing container, and it is so designed that no gaps are defined among the plurality of shield members. Furthermore, the liquid-storing shield member can also be formed into a shape of an on-liquid- floatable type pyramidal body having a hexagonal bottom face.