Please cite this article as: A. Suzuki, H. Yukawa, T. Nambu, Y. Matsumoto, Y. Murata, Analysis of hydrogen mobility in Nb-based alloy membranes in view of new description of hydrogen permeability based on hydrogen chemical potential, Journal of Alloys and Compounds (2015), doi: http://dx.ABSTRACT The hydrogen permeability of Nb-based alloy membranes have been analyzed in view of the new description of hydrogen permeation based on hydrogen chemical potential in order to investigate the alloying effects on the mobility of hydrogen atom, B. There is a liner relationship between the normalized hydrogen flux, J L, and the PCT factor, f PCT . The mobility of hydrogen atom is expressed in a format of the Arrhenius equation. Then, the alloying effects on the activation energy,E, and the pre-exponential factor, B 0 , have been investigated. It is found that logarithm of the pre-exponential factor, lnB 0 , is proportional to the activation energy, E. In other words, when one factor decreases by alloying, the other factor also decreases linearly. As a result, the addition of ruthenium, tungsten and molybdenum into niobium enhances the hydrogen diffusivity at low temperature below the intersection temperature, T int .