The rate of oxygen removal from an oxygen-doped Nb membrane by hydrogen ion sputtering was examined by measuring the change in the sticking coefficient of H2, α. First, the temperature dependence of α was measured at various oxygen concentrations to investigate correlation between bulk oxygen concentration and α. Then the oxygen concentration in the membrane was adjusted to 1.5 at%, and the surface of the membrane was irradiated by hydrogen ions of 600 eV at 1113 K. The change in α with sputtering time was measured, and the reduction in bulk oxygen concentration was estimated from the extent of change in α. The oxygen concentration decreased with increasing sputtering time by continuous surface segregation of oxygen and sputtering. The sputtering yield of oxygen on the Nb membrane surface was evaluated to range from 0.012 to 0.036
