A nickel-metal hydride storage battery having a high capacity and excellent cycle life is disclosed. The battery employs, as its material for the negative electrode, a hydrogen storage alloy powder having a composition represented by the general formula Zr.sub.1-x M3.sub.x Mn.sub.a Mo.sub.b Cr.sub.c M1.sub.d M2.sub.e Ni.sub.f, where M1 represents at least one element selected from the group consisting of V, Nb and rare earth elements, M2 represents at least one element selected from the group consisting of Fe, Co and Cu, and M3 represents at least one element selected from the group consisting of Ti and Hf, and where 0.ltoreq.x.ltoreq.0.3, 0.3.ltoreq.a.ltoreq.0.7, 0.01.ltoreq.b.ltoreq.0.2, 0.05.ltoreq.c.ltoreq.0.3, 0.ltoreq.d.ltoreq.0.1, 0.ltoreq.e.ltoreq.0.2, 0.8.ltoreq.f.ltoreq.1.3, and 1.6.ltoreq.a+b+c+d+e+f.ltoreq.2.2, and wherein said hydrogen storage alloy has at least one of a Laves phase having a crystal structure of the MgCu.sub.2 -type (C15) and a Laves phase having a crystal structure of the MgZn.sub.2 -type (C14), and wherein a sum of integrated intensities of diffraction peaks other than those attributed to the presence of said Laves phase is not more than 5% of a sum of integrated intensities of all diffraction peaks in a diffraction angle 2.theta. of 10.degree. to 80.degree. in a powder X-ray diffraction pattern by Cu K.alpha. radiation.