A positive electrode active material for a non-aqueous electrolyte secondary battery, including primary particles of a lithium nickel composite oxide represented by the formula: Li b Ni 1-x-y Co x M y O 2 wherein M represents at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr and Mo; b represents a number satisfying 0.95 ‰¤ b ‰¤ 1.03; and x represents a number satisfying 0 < x ‰¤ 0.15 and y represents a number satisfying 0 < y ‰¤ 0.07, wherein the sum total ofx and y is 0.16 or smaller, i.e., x+y ‰¤ 0.16) and secondary particles that are aggregates of the primary particles, wherein microparticles containing W and Li are present on the surface of each of the primary particles, and the length of axis-c of the lithium nickel composite oxide is 14.183 angstroms or more as determined by a Rietveld analysis of X-ray diffraction data on the oxide.