Disclosed is a transformant prepared by introducing a ketoreductase gene involved in the biosynthesis of L-epivancosamine into an actinobacterium originally capable of producing daunorubicin. Also disclosed is a process of efficiently producing a non-natural daunorubicin derivative using the transformant. The transformant is capable of efficiently producing a non-natural daunorubicin derivative such as epidaunorubicin.