The rates of ab/desorption of water vapor for Zr-V-Fe getter were investigated by means of mass analyzed thermal desorption spectroscopy. The absorption rate obeyed first order kinetics with respect to the pressure of water vapor. The activation energies for absorption were determined as 1.8 (H2O), 2.7 (D2O), and 3.2 (T2O) kcal/mol. Only hydrogen was desorbed by heating the getter in which water was absorbed. The desorption obeyed second order kinetics with respect to the amount of absorption. The activation energies for desorption were determined as 28.0 (H2O), 28.6 (D2O), and 29.3 (T2O) kcal/mol. It is concluded that the rate determining step for absorption is the dissociation reaction of adsorbed water molecules or hydroxyl groups on the surface. The rate determining step for desorption is the association reaction of hydrogen atoms which diffuse from the bulk to the surface.