PROBLEM TO BE SOLVED: To provide a conductive polymer solution and conductive polymer material which can inhibit the occurrence of unreacted material, have the improved expression of conductivity, and also have sufficient water resistance, and a solid electrolytic capacitor and a method of producing the same.SOLUTION: This invention provides a conductive polymer solution at least comprising a conductive polymer, at least one of water and water-miscible organic solvent, dopant, polyvalent alcohol, and water-soluble polycarboxylic acid, with at least part of the water-soluble polycarboxylic acid comprising a sulfo group.