Abstract: The present invention provides a conductive polymer in which, when being formed into a coating film, foreign materials are difficult to be generated even the passage of time and a quality control method for a conductive polymer and has a repeating unit which is represented by the following general formula (1). The present invention also provides a quality control method for conductive polymers wherein conductive polymers with an area ratio (Y/X) of 0.60 or less are selected. In the formula R1 to R4 are each independently —H, a linear or branched alkyl group having 1 to 24 carbon atoms, a linear or branched alkoxy group having 1 to 24 carbon atoms, an acidic group, a hydroxyl group, a nitro group, —F, —Cl, —Br or —I; and at least one of R1 to R4 is an acidic group or a salt thereof.