An electrochemical steam pump was operated at temperatures of 700-900 degrees C using a high-temperature type protonic conductor, SrCe0.95Yb0.05O3-alpha, as a solid electrolyte. When wet air and dry air were introduced into the anode and cathode, respectively, and direct current was applied to the solid electrolyte, the partial pressure of water vapour decreased at the anode, while it increased at the cathode. At low current densities, the pumping rate of water vapour was increased by decreasing the operating temperature and increasing the partial pressure of water vapour at the anode. This is due to the change in proton transport number in SrCe0.95Yb0.05O3-alpha which depends on the operating condition. At high current densities, the pumping rate was limited by the diffusion rate of water vapour through the porous anode.