Amphoteric-charged poly(acrylonitrile) (PAN) membranes possessing both carboxyl and tertiary amine groups were prepared by radical graft polymerization. By varying the molar ratio of acidic to basic monomers, we could obtain four kinds of amphoteric-charged membranes. These membranes were systematically analyzed by Fourier transform infrared spectroscopy/attenuated total reflection (FT-IR/ATR) regarding the effects of feed monomer composition and pH change. Also, the spectra acquired were qualitatively compared with our previous electrokinetic data. From these results, it was found that the spectral difference among the amphoteric-charged PAN membranes can be characterized by salt formation between the carboxyl group and the adjacent tertiary amine group on the graft chains and/or sodium ions; the larger the tertiary amine group fraction, the more carboxyl groups take the ionized form.