A lithium secondary battery which comprises: a negative electrode comprising as an active material a carbonaceous material capable of electrochemically holding/releasing lithium; a positive electrode comprising as an active material a lithium chalcogenide; and polymer electrolyte layers united respectively with the negative electrode and the positive electrode. The polymer electrolyte layers comprise an ionically conductive polymer matrix holding a nonaqueous electrolytic solution. They are obtained by crosslinking and polymerizing a liquid mixture of a monomeric precursor for the ionically conductive polymer and the nonaqueous electrolytic solution respectively on the negative electrode and the positive electrode using different polymerization initiators.