A novel α-1,3-fucosyltransferase which is expressed by the gene cloned from animal cells; a cDNA coding for the transferase; a method of detecting α-1,3-fucosyltransferase using the cDNA and inhibiting the production of the transferase; a recombinant vector containing the cDNA integrated thereinto; a cell containing the vector; and processes for producing the above. The α-1,3-fucosyltransferase invented is useful for producing physiologically active sugar chains, such as sialylated Lewis X, and modifications thereof.