Provided is a lithium ion secondary cell which comprises a layered body obtained by alternately layering electrode plates having terminal tabs and semisolid or solid electrolyte layers, and a sheet-like outer packaging inside of which the layered body is enclosed and sealed with the terminal tabs partially projecting out, and the lithium ion secondary cell is characterized in that the outer packaging has a layered body-contiguous sealing part that is contiguous with at least a portion of the edges of the layered body and thereby seals the layered body.