PURPOSE: To increase the amt. of hydrogen to be stored and to reduce the hysteresis in the hydrogen storage alloy by limiting the componental compsn. of an alloy constituted of rare earth elements, Ni, Al, Fe, Cu, Nb, Si and Zr to the range shown by prescribed rational formula.

CONSTITUTION: The rare earth metal-series hydrogen storage alloy is formed from the componental compsn. shown by rational formula RemNiWAlXFeYMZ (where Rem denotes one or more kinds selected from rare earth elements and M denotes one or more kinds selected from Cu, Nb, Si and Zr as well as 2.5 to 5.5 W, 0 to 2 X, 0 to 2 Y, 0 to 2 Z and 4 to 6 W+X+Y+Z are regulated). The above alloy has high hydrogen occluding capacity and has reduced hysteresis, i.e., the difference between the occluding pressure and dissociation pressure in hydrogen.