2-Hydroxyisoflavanone dehydratase substantially having the amino acid sequence represented by SEQ ID NO: 1 is isolated from licorice. Further, a polynucleotide encoding 2-hydroxyisoflavanone dehydratase of the SEQ ID NO: 2 is obtained. Furthermore, the amino acid sequence of 2-hydroxyisoflavanone dehydratase is identified from soybean and a polynucleotide encoding 2-hydroxyisoflavanone dehydratase is obtained.