A positive electrode active material for a lithium ion secondary battery, including a lithium-nickel composite oxide having a hexagonal layered structure and configured by particles including at least either single primary particles or secondary particles with a plurality of aggregated primary particles, wherein the particles included in the positive electrode active material have a cross section having one or more crystal faces, and the one or more crystal faces in the particles have an average misorientation of 0.7° or less from a reference orientation of each of the one or more crystal faces.