Novel electrical conductive carbon nanofibers were prepared by a combination of electrospinning and ion-beam irradiation techniques. Four types of polymer nanofibers, including polyimides (2,2'-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA)-2,2'-bis(4-aminophenyl) hexafluoropropane (6FAP) and 6FDA-Bis(4-(4-aminophenoxy) phenyl) sulfone (APPS)), polysulfone (PSF) and polyacrylonitrile, were prepared by the electrospinning method, which yielded fine nanofibers with diameters of similar to 150nm (except PSF) under optimized conditions. The obtained polymer nanofibrous membranes were irradiated with Kr+ using an ion implanter at various ion fluences to give carbonized nanofibers. The electrical conductivities of the carbon nanofibers increased with an increase in the ion fluence; the conductivity of the electrospun 6FDA-6FAP nanofibrous membrane reached up to ca. 10(-1)S cm(-1) with 10(16) ion cm(-2) of Kr+. The influence of the starting polymers on the electrical conductivity of the carbon nanofibers was studied by Raman and X-ray photoelectron spectroscopy analyses.