A continuous hydrogen isotope separation system using twin beds of metals or alloys is here proposed. The isotope separation system called a twin-bed periodically counter-current flow (TB-PCCF) is analytically and experimentally investigated. Palladium and LaNi4.7Al0.3 were selected based on experimental data of the isotope separation factor and the isotopic exchange rate. Numerical calculations by a plate model revealed effectiveness of the TB-PCCF method which is composed of an enriching column packed with Pd particles and a stripping column packed with LaNi4.7Al0.3 particles. A preliminary experiment was performed at the condition where absorption and desorption cycles are repeated between room temperature and 473K for Pd and 363K for LaNi4.7Al0.3 at the total reflux, and it showed possibility of the hydrogen isotope separation.