In the electrochemical hydrogen pump based on SrCe0.95Yb0.05O3-alpha proton conductor cell, effects of water vapor supplied to the cathode and operation temperature on the pumping characteristics were examined. Hydrogen-pumping capacity could be enhanced by increasing water vapor supply to the cathode and by reducing operation temperature within the examined range of 700-900 degreesC. Presence of sufficient water vapor at the cathode would keep the current efficiency of the hydrogen pump.