Abstract: A cell comprising a casing, a roll electrode element accommodated in said casing, and an electrolyte filled into the casing, the roll electrode element being composed of at least one sheet-like positive electrode, at least one sheet-like negative electrode and at least one film separator which are arranged alternately in an overlapped relation to each other such that the sheet-like positive electrode is brought into contact with the sheet-like negative electrode through the separator film, to form an electrode laminate, wherein the electrode laminate is wound around a core having an approximately rhombic shape in section to form a roll having a multi-layered structure and, after removal of the core, the roll of the electrode laminate is compressed to obtain the roll electrode element having an ellipsoidal shape in section.