To provide a method of preparing conductive polymers having a reduced content of metal salts and high conductivity.

The method comprises polymerizing (C) a polymerizable monomer capable of producing a polymer having conjugated double bonds with an oxidation catalyst consisting of (A) an imide compound e.g. N- hydroxyphthalimide, and optionally (B) a cocatalyst comprising a metal compound and/or a boron compound to obtain (D) a conductive polymer.