An active material for positive electrode for a non-aqueous electrolyte secondary battery comprises a lithium-metal composite oxide that is expressed by the general formula of Li.sub.x(Ni.sub.1-yCo.sub.y).sub.1-zM.sub.zO.sub.2 (where 0.98.ltoreq.x.ltoreq.1.10, 0.05.ltoreq.y.ltoreq.0.4, 0.01.ltoreq.z.ltoreq.0.2, and where M is at least one metal element selected from the group of Al, Mg, Mn, Ti, Fe, Cu, Zn and Ga), and where the SO.sub.4 ion content is in the range from 0.4 weight % to 2.5 weight %, and the occupancy rate of lithium found from the X-ray diffraction chart and using Rietveld analysis is 98% or greater, and the carbon amount measured by way of the high frequency heating-infrared adsorption method is 0.12 weight % or less, and that the Karl Fischer water content due to heating at 180.degree. C. be 0.2 weight % or less.