An object of the present invention is to modify a wild-type enzyme that is less reactive in the presence of an organic solvent to provide altered carbonyl reductases having better reactivity in the presence of the organic solvent than the wild-type enzyme, and/or to provide transformants producing such reductases. The present inventors have found altered carbonyl reductases having better reactivity in the presence of an organic solvent than the wild-type enzyme, from among a mutant enzyme library prepared by randomly mutating the wild-type enzyme gene, thereby arriving at completion of the present invention.