[Object] To provide an FAD-conjugated glucose dehydrogenase having a higher specificity for glucose.[Means for Resolution] A modified glucose dehydrogenase (GLD) which includes a substitution of at least one amino acid residue selected from the group consisting of amino acid residues at positions 37, 69, 72, 73, 76, 78, 102, 217, 228, 240, 356, 407, 424, 437, 527, and 530 in an amino acid sequence of a wild-type FAD-conjugated glucose dehydrogenase (GLD) represented by SEQ ID NO: 1, and has a decreased ratio of activity for xylose/activity for glucose as compared with the wild-type GLD; a polynucleotide encoding the modified GLD; a recombinant vector containing the polynucleotide; a transformed cell produced by using the recombinant vector; etc.