An electrochemical hydrogen pump using the SrCe0.9Yb0.05O3-x proton conductor has been applied to hydrogen extraction and production. The extraction of hydrogen from dilute hydrogen and synthesis gases, and hydrogen production by water vapor electrolysis are demonstrated. The extraction of hydrogen could be operated with a current efficiency close to unity, while some electronic conduction appeared in the water vapor electrolysis. The introduction of water vapor into the cathode compartment was effective to extend the current density. These results, together with the problems to be solved, are mainly discussed in terms of electrode reactions and ionic transport numbers.