A new hydrogen isotope separation system has been experimentally studied to concentrate deuterium from natural hydrogen. The present system comprises four columns packed with Pd particles and is operated in such a way that Pd particles and a hydrogen isotope gas flow simulated countercurrently. Deuterium is concentrated at the top end of the column at room temperature and atmospheric pressure. The deuterium concentration increases with an increase in the number of passages through the columns. When a 0.00996 in molar fraction D-2 + 0.994 H-2 mixture or natural hydrogen with 0.00015 D in atomic molar fraction was passed through 16 columns, the maximum atomic molar fraction of deuterium at the column top end were 0.728 or 0.0508, respectively.