Cryogenic adsorption is effective for the separative recovery of hydrogen isotopes of small concentrations from the bulk helium gas. Thus, the cryogenic adsorption method is considered to be applied to the recovery of tritium from the blanket sweep gas which recovers tritium from ceramic breeder materials, the cleanup system of the helium discharge exhaust gas of the fusion reactor and so forth. The authors performed a screening test to find more suitable adsorbents for the recovery of hydrogen isotopes from the bulk helium gas at liquid nitrogen temperature. The authors tested various adsorbents, and the screening test indicates that a natural mordenite adsorbent has a quite high adsorption capacity for hydrogen under the helium atmosphere. For the adsorption of deuterium, it was found that the natural mordenite adsorbent have a high adsorption capacity even at lower pressure range of deuterium. The adsorption rate of hydrogen isotopes was quantified by analyzing breakthrough curves obtained in the experiments. Evaluated effective pore diffusivities of hydrogen isotopes in the mordenite adsorbents are comparable to that in MS5A adsorbents. Thus, it can be said that mordenite adsorbents are also suitable for adsorption of hydrogen isotopes from the viewpoint of adsorption rates. The results mentioned above suggest that the mordenite-type of adsorbents is promising for the recovery of low-concentration hydrogen isotopes from the helium bulk gas.