To provide a gel electrolyte formable sheet and a gel electrolyte support sheet which are better in mechanical strength, difficult to cause an internal short circuit and lower in internal resistance (higher in ionic conductivity), and a lithium secondary battery using the sheets.

The gel electrolyte formable sheet includes resin which can gel by a specific nonaqueous solvent and resin which can not gel by the nonaqueous solvent, and comprises a fiber sheet substantially constituted by a surface gelation composite fiber wherein the resin that can gel occupies at least a part of a fiber surface. The gel electrolyte support sheet is provided by causing the resin of the surface gelation composite fiber that can gel to gel by the specific nonaqueous solvent using the gel electrolyte formable sheet. The lithium secondary battery uses the gel electrolyte support sheet.