Anhydrous proton-conductive membranes are prepared by incorporating sulfuric acid (H2SO4) into cross-linked poly(4-vinylpyridine) (CL-P), where H2SO4 mixes CL-P homogeneously at the molecular level, and therefore incorporated H2SO4 does not leach out from CL-P, even when the weight ratio of H2SO4 to CL-P is about four. The membranes are soft but self-standing and exhibit anhydrous conductivity higher than 100 mS cm-1 at around 100 °C. Furthermore, a membrane composed of polystyrene-b-poly(4-vinylpyridine)-b-polystyrene triblock copolymers and H2SO4 achieves not only high anhydrous conductivity but also good mechanical properties as a membrane.