Hydrogen storage alloy has: (1) a main composition expressed by the formula of Mm-(Ni-Al-Co-Mn-Cu); (2) a ratio of the number of atoms expressed by the formula (Ni-Al-Co-Mn-Cu) is 5.5<(Ni+Al+Co+Mn+Cu)7.0, and 4.0Ni, when Mm is set at 1 in a ratio of the number of atoms; and (3) an internal structure having hydrogen storage alloy phase expressed by the general formula of AB₅ and a second phase existing in the hydrogen storage alloy phase, wherein the whole the composition is expressed by the formula of MmiNi_(3.95+p)Al_(0.3+q)Co_(0.4+r)Mn_{(0.45+s)Cu(0.10+t)}, and 0.3<(p+q+r+s+t)1.8.