A process for producing a glycoprotein composition improved in the amount of sialic acid added to the sugar chain; a method of culturing a cell producing a glycoprotein composition improved in the amount of sialic acid added to the sugar chain; a method of improving the amount of sialic acid to be added to the sugar chain of a glycoprotein composition; and a method of reducing the content of N-glycolylneuraminic acid in a glycoprotein composition.
