Provided is a method for manufacturing an active material composite powder by which an active material composite powder that can inhibit increase in its reaction resistance at a high voltage state can be manufactured. The method includes: spraying a solution containing lithium and a peroxo complex of niobium to an active material, and at the same time drying the solution; carrying out a heating treatment, after the spraying and drying, for obtaining a powder including the active material and a coating layer attached to a surface of the active material; producing a mixed liquid by mixing the powder and a solvent that can dissolve lithium nitrate and does not dissolve lithium niobate included in the coating layer obtained by the heat treatment, and stirring the mixed liquid; and carrying out, after the mixing and stirring, a solid-liquid separation on the mixed liquid; and drying a solid obtained by the separation.