NOVELTY - Magnesium-nickel-containing master alloy is manufactured by dissolution and casting process. The obtained master alloy is heated at 600 degrees C for 1-20 hours directly under melting point of master alloy. The resultant material is cooled at the cooling rate of 5 degrees C/minute or less to obtain battery hydrogen storage alloy having 90 area% or more of lanthanum-magnesium-nickel-type crystal phase having 2H-type laminated structure and lanthanum-magnesium-nickel-type crystal phase having 3R laminated structure.    USE - Manufacture of hydrogen storage alloy used for nickel-hydrogen secondary battery used as power supply for hybrid vehicle and electric vehicle.    ADVANTAGE - The hybrid vehicles using hydrogen storage alloy have excellent fuel consumption property. The nickel-hydrogen secondary battery using hydrogen storage alloy has high capacity and discharging characteristics.    DETAILED DESCRIPTION - Magnesium-nickel-containing master alloy (A1-aMgaNibMcXd, where A is lanthanum, cerium, praseodymium, neodymium and/or samarium, M is iron, cobalt, manganese, copper, titanium, zirconium, vanadium, niobium, tantalum, chromium, molybdenum, and/or tungsten, X is aluminum, gallium, zinc, tin, silicon, boron, carbon and/or phosphorus, a is more than 0 to less than 0.25, b is 3-4, c is 0-1, d is 0.1-1, and b+c+d is 3.6-4.05) is manufactured by dissolution and casting process. The obtained master alloy is heated at 600 degrees C for 1-20 hours directly under melting point of master alloy. The resultant material is cooled at the cooling rate of 5 degrees C/minute or less to obtain battery hydrogen storage alloy having 90 area% or more of lanthanum-magnesium-nickel-type crystal (La3MgNi14) phase having 2H-type laminated structure and lanthanum-magnesium-nickel-type crystal (La2MgNi9) phase having 3R laminated structure.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view preferred nickel-hydrogen secondary battery.    Hydrogen storage alloy electrode (11)    Separator (13)    Container (14)    Sealing board (16)    Insulating gasket (17)