The migration of hydrogen ions dissolved in SrCeO3 induced by an applied electric potential has been studied over the temperature range from 25 to 200 degrees C. It was found that the hydrogen ions migrated towards the cathode, and they were trapped there when the cathode material had a good ability to getter the hydrogen. The amounts of hydrogen retained in the cathode could be determined by the ERDA technique using a high-energy He-4 beam. In order to estimate the proton transport number, defined as the ratio of the protonic conductivity to the total electric conductivity, we measured the amount of hydrogen retained in the cathode as a function of electric charge number through the specimen. The protonic conductivity and the proton diffusion coefficient were evaluated using the proton transport number and proton concentration in the specimen.