Abstract: A zirconium alloy having a plateau region of equilibrium hydrogen dissociation pressure and a small hysteresis, whose hydrogen dissociation pressure is in a range of 0.6 to 3 atm at 20.degree. C., 1 to 5 atm at 40.degree. C., and 1 to 17 atm at 80.degree. C., the activation of which can be effected according to a single procedure of vacuum evacuation at room temperature and pressurization under a hydrogen pressure of 30 atm at room temperature, and which is comparable or superior in the rates of hydrogen absorption and release, the maximum hydrogen absorbing capacity and effective hydrogen releasing capacity to conventional zirconium alloys. A hydrogen absorbing and releasing material comprising an alloy as mentioned above and thin films of one element selected from Pd, Cu, and Ni, which allows only hydrogen to permeate, and covering the surfaces of particles of the alloy.