Abstract: A method for preparing an ultrafine powder, which comprises forming a precipitate by reacting a hydroxide type precipitate-forming agent to an aqueous solution containing at least one type of metal ions capable of forming a hydroxide type precipitate which forms a stable floc in the presence of sulfate ions, adding sulfate ions before or after forming the precipitate, to let the formed precipitate form a stable floc, and then dispersing the precipitate in an organic solvent without drying it, followed by drying to obtain independently separated amorphous or crystalline primary particles having an average particle size of at most 0.2 .mu.m.