There are provided a positive electrode active material for an alkaline storage battery, a positive electrode for an alkaline storage battery, and an alkaline storage battery each of which has an excellent output characteristics and also has an excellent self-discharge characteristic and an excellent cycle lifetime characteristic. The positive electrode active material for an alkaline storage battery according to the present invention has nickel hydroxide particles each containing at least magnesium in a solid solution state and a cobalt compound layer coating the surface of each of the nickel hydroxide particles. Among them, the cobalt compound layer contains cobalt having an average valence of not less than 2.6 and not more than 3.0 and also contains sodium at a proportion of less than 0.10 wt % to the total weight of the cobalt compound layer. The positive electrode active material for an alkaline storage battery according to the present invention has a conductivity smaller than 1.0×10−5 S/cm in a state pressurized at 39.2 MPa.