Disclosed is a method for preparing a highly electron conductive polymer, the method comprising a step of doping a conductive polymer with a dopant capable of introducing movable charge carriers into the repeating units of the polymer, wherein a voltage higher than a conduction band of the polymer is applied to the polymer while the polymer is doped with the dopant, so as to modify electron conductivity of the conductive polymer. A highly electron conductive polymer obtained by the method, an electrode comprising the highly electron conductive polymer, and an electrochemical device including the electrode arc also disclosed. The novel doping method for improving the electron conductivity of a conductive polymer can provide a conductive polymer with a conductivity comparable to the conductivity of a conventional conductive agent.