The present invention relates to a method of producing an optically active pyridineethanol derivative. More particularly, it relates to a method of producing an optically active polycyclic pyridineethanol derivative by causing an enzyme or enzyme source to act on polycyclic acetylpyridine derivatives.The present invention also relates to a novel enzyme which can be used in the production method mentioned above, a DNA coding for said enzyme, a recombinant vector having said DNA, and a transformant having said recombinant vector.The invention further relates to a method of producing an optically active polycyclic pyridineethanol derivative by causing the above novel enzyme or the above transformant to act on optically inactive polycyclic pyridineethanol derivatives.