Abstract: A water-soluble composition comprising (A) coenzyme Q10 of 5-40% by weight, (B) monoester of polyglycerol with average polymerization degree of 10 and fatty acid with 18 carbon atoms of 5-30% by weight, (C) mono-, di-, tri- or penta-ester of polyglycerol with average polymerization degree of 3-6 and fatty acid with 18 carbon atoms of 1-18% by weight, and (D) water, wherein its average particle diameter is 110 nm or smaller. It is superior in acid resistance, salt-resistance and heat resistance, and further enables to maintain the good water-soluble state being blended to medicines, foods and beverages, cosmetics, feeds, additives usually employed therein.