[Object] To provide a conductive polymer solution capable of forming a capacitor having a large capacitance, low ESR, and excellent long-term reliability without using treatment solutions for conductive polymer layer formation differing in composition, and without forming an inside conductive polymer layer by different approaches, the capacitor and a method for producing the capacitor [Solution] The present invention relates to: a conductive polymer solution which comprises a conductive polymer and a solvent, wherein the conductive polymer comprises a pi-conjugated conductive polymer, a polyanion with which the pi-conjugated conductive polymer has been doped, and a compound formed by reacting an oxirane or oxetane group with an anion making no contribution to the dope in the polyanion, and the solution has a pH in the range of 2.0 to 6.0; a capacitor which includes either the conductive polymer solution or the compounds remaining after removal of the solvent from the solution; and a method for producing a capacitor, comprising impregnating the capacitor with the conductive polymer solution and removing the solvent therefrom.