Abstract: A surface polyaniline layer comprising a polyaniline and/or a derivative thereof capable of generating active oxygen or hydrogen peroxide upon the reaction with the water component in external air that comes in contact therewith, is formed on at least a portion of the outermost surface of a base body constituting tubes and/or fins, wherein a benzenoid/quinoid ratio in the surface polyaniline layer (defined as a ratio of an absorbancy of the benzenoid structure to an absorbancy of the quinoid structure in the polyaniline and/or the derivative thereof) is in a range of about 0.5 to about 3.0.