A hydrogen storage alloy having a crystal structure in which an AB 2 type unit and an AB 5 type unit are laminated, a characteristic diagram including a hydrogen solid solution region, a hydride region, a first plateau region and a second plateau region, the characteristic diagram indicating a relation between a hydrogen storage amount and a hydrogen pressure at 80°C, the hydrogen solid solution region being a region in which the hydrogen pressure changes at a first slope with respect to change in the hydrogen storage amount, the hydride region being a region in which the hydrogen pressure changes at a second slope with respect to the change in the hydrogen storage amount, the first plateau region being a region in which the hydrogen pressure changes at a smaller slope than the first slope and the second slope with respect to the change in the hydrogen storage amount and that has a hydrogen pressure Pd1 when hydrogen is stored by 0.25 times an effective hydrogen storage amount that is a hydrogen storage amount when the hydrogen pressure is 1 MPa, the second plateau region being a region in which the hydrogen pressure changes at a smaller slope than the first slope and the second slope with respect to the change in the hydrogen storage amount and that has a hydrogen pressure Pd2 when the hydrogen is stored by 0.70 times the effective hydrogen storage amount that is the hydrogen storage amount when the hydrogen pressure is 1 MPa, the hydrogen pressure Pd1 and the hydrogen pressure Pd2 satisfying a relation of 0.6 ≤ log 10 (d2/Pd1), wherein the hydrogen storage alloy has a composition expressed by a general formula: Ln 1-x Mg x Ni y-z-α Al z M α (in the formula, Ln represents at least one element selected from the group consisting of Zr and rare earth elements, M represents at least one element selected from the group consisting of V, Nb, Ta, Cr, Mo, Fe, Ga, Zn, Sn, In, Cu, Si, P and B, and suffixes x, y, z and α satisfy relations of 0 ≤ x < 0.03, 3.3 ≤ y ≤ 3.6, 0.2 ≤ z ≤ 0.4 and 0 < α ≤ 0.1, respectively). a characteristic diagram including a hydrogen solid solution region, a hydride region, a first plateau region and a second plateau region, the characteristic diagram indicating a relation between a hydrogen storage amount and a hydrogen pressure at 80°C, the hydrogen solid solution region being a region in which the hydrogen pressure changes at a first slope with respect to change in the hydrogen storage amount, the hydride region being a region in which the hydrogen pressure changes at a second slope with respect to the change in the hydrogen storage amount, the first plateau region being a region in which the hydrogen pressure changes at a smaller slope than the first slope and the second slope with respect to the change in the hydrogen storage amount and that has a hydrogen pressure Pd1 when hydrogen is stored by 0.25 times an effective hydrogen storage amount that is a hydrogen storage amount when the hydrogen pressure is 1 MPa, the second plateau region being a region in which the hydrogen pressure changes at a smaller slope than the first slope and the second slope with respect to the change in the hydrogen storage amount and that has a hydrogen pressure Pd2 when the hydrogen is stored by 0.70 times the effective hydrogen storage amount that is the hydrogen storage amount when the hydrogen pressure is 1 MPa, the hydrogen pressure Pd1 and the hydrogen pressure Pd2 satisfying a relation of 0.6 ≤ log 10 (d2/Pd1), wherein the hydrogen storage alloy has a composition expressed by a general formula: Ln 1-x Mg x Ni y-z-α Al z M α (in the formula, Ln represents at least one element selected from the group consisting of Zr and rare earth elements, M represents at least one element selected from the group consisting of V, Nb, Ta, Cr, Mo, Fe, Ga, Zn, Sn, In, Cu, Si, P and B, and suffixes x, y, z and α satisfy relations of 0 ≤ x < 0.03, 3.3 ≤ y ≤ 3.6, 0.2 ≤ z ≤ 0.4 and 0 < α ≤ 0.1, respectively).