The current-voltage curves of a composite bipolar membrane (CBM) were experimentally measured by varying the interface component between cation- and anion-exchange membranes for water and methanol solutions. In each solution system, 0.05 mol/l LiCl was used as the electrolyte. The interface component was varied by pasting the polymers or installing the thin membranes in the intermediate region of the CBM. The measured results show that the functional groups of the polymers and thin membranes enhanced the water and methanol splitting effect. This phenomenon can be explained by the protonation-deprotonation reactions occurring between these functional groups and the water or methanol molecules in the intermediate region of the CBM. The effect of transition metal compounds existing in the intermediate region of the CBM was also experimentally examined in this study. It was found that the effect of transition metal compounds on water or methanol splitting was not obvious.