Hydrogen diffusivity (D) and permeability (q) in Pd50-xTi50(Cr, Fe)x alloys were measured at temperature range between 570 and 770 K. During a heating measurement of Pd47Ti50Cr3 alloy, both D and q abruptly increased by factors of 5 and 2, respectively, at 712 K, with a phase transformation from B19 to B2 structures. However, q was far smaller than those in pure bcc metals (eg. V, Nb and Ta), where the hydrogen atoms occupy the tetrahedral interstitial sites. A first-principles calculation revealed that hydrogen atoms occupy the octahedral interstitial sites in Pd50Ti50 with B2 structure. It is concluded that the small hydrogen diffusivity in B2 Pd50-xTi50(Cr, Fe)x alloys is due to the long distance hydrogen jump and the resultant high activation energy for the diffusion.