Disclosed is a flavin-bound glucose dehydrogenase having high substrate specificity to D-glucose. Specifically disclosed is a novel flavin-bound glucose dehydrogenase derived from a microorganism belonging to genus Mucor. The flavin-bound glucose dehydrogenase is characterized by having lower reactivity to maltose, D-galactose and D-xylose compared to the reactivity to D-glucose and being rarely affected by these sugar compounds. The flavin-bound glucose dehydrogenase is rarely affected by dissolved oxygen and enables the accurate determination of the quantity of glucose in a sample even when a sugar compound other than glucose is present in the sample.
