Disc-type and powder-type electrodes of hydrogen storage alloys having the compositions MmNi(4.2)Al(0.5)M(0.3)(Mm = misch metal; M = Cr, Mn, Fe, Co, Ni) were used for the evaluation of diffusion coefficients of hydrogen by the potential-step method and the electrochemical measurement of the pressure-composition isotherm respectively. The Einstein diffusion coefficient, being independent of hydrogen concentration, was measured as a function of the atomic radius of foreign metals(M). The diffusion kinetics of the hydrogen atom in the alloys was discussed based on the thermodynamic stability of the resulting hydrides and electrostatic interaction between foreign metals and hydrogen.