Provided is an alkaline storage battery exhibiting large discharge capacity and little performance degradation during over-discharge. A positive electrode active material for an alkaline storage battery has: a core layer containing nickel hydroxide; and a conductive auxiliary layer coating the surface of the core layer. The positive electrode active material is characterized by the conductive auxiliary layer containing a cobalt oxyhydroxide phase and a cerium dioxide phase, and by the active material containing lithium. The inclusion of the cerium dioxide phase in the conductive auxiliary layer enables the inhibition of the reduction of the cobalt oxyhydroxide phase, even in conditions such as over-discharge. The inclusion of lithium in the active material and the inclusion of cerium dioxide in the conductive auxiliary layer enable the increase of the battery discharge capacity.