A secondary battery comprising an electroconductive polymer as an electrode active material for a positive electrode (1), a lithium alloy as a negative electrode (2), and an electrolytic solution composed of a solvent mixture of propylene carbonate and an ether-based solvent containing a lithium complex salt in a dissolved state, the polymer comprising polyaniline having an aniline structure in the main chain where doping of anions from the electrolytic solution is carried out at charging and undoping of the anions is carried out at discharging has a low self discharge rate and a long charge-discharge cycle life.