Disclosed is a sealed alkaline storage battery with an increased utilization of a positive electrode active material comprising a nickel oxide and with drastically enhanced capacity density. The positive electrode active material is a nickel based multi-metals oxide containing at least one element such as Mn which promotes the formation of .gamma. phase during charging. The ratio A.sub..gamma. /A.sub..beta. of the integrated intensity A.sub..gamma. of the diffraction peak at d=about 7 angstroms attributed to the .gamma. phase to the integrated intensity A.sub..gamma. of the diffraction peak at d=about 4.5 to 5.0 angstroms attributed to the .beta. phase of the oxide in the completely charged state is not smaller than 0.4. The electrolyte comprises an aqueous solution containing at least one of K.sup.+ and Na.sup.+ as a cationic component and the total concentration of the above-mentioned cationic component in the completely charged state is within a range between 4 and 12 mol/l.