A cell in which the activity of a protein relating to transport of an intracellular sugar nucleotide, GDP-fucose, to the Golgi body is more decreased or deleted than its parent cell; a process for producing an antibody composition using the cell; a transgenic non-human animal or plant or the progenies thereof, in which genome is modified so as to have a decreased or deleted activity of a protein relating to transport of an intracellular sugar nucleotide, GDP-fucose, to the Golgi body; a process for producing an antibody composition from the animal or plant; and a medicament comprising the antibody composition.