An electrochemical pump consisting of poly(acrylic acid) incorporating Cu2+ ion was developed. The pump discharges and charges liquid at the level of a few hundred of picoliter per second upon expansion and contraction of the gel induced by reduction and oxidation of the copper, respectively. The pump discharged ca. 5 μl of water at -1.3 V vs. Ag/AgCl for 3 h, whereas charged ca. 1.2 μl at +1.0 V for 3 h. At constant currents of -4.4 and +4.4 μA cm-2, the volumes of water discharged and charged were found to be nearly proportional to the charge at ca. 0.10 cm3 C-1 for both reduction and oxidation processes, except for an initial stage of the electrolysis. Further, upon repeated galvanostatic electrolyses, the same volume-charge slopes were obtained. These results indicate a reversibility and reproducibility of the pump.