New anthracycline antibiotics of a formula (I) are provided, which are usable as an anticancer agent ##STR1## (where R represents a hydrogen atom or a hydroxyl group). The antibiotics (I) can be produced by incubation of a dye-nonproductive or hardly dye-productive mutant strain which has an ability of converting .alpha.-citromycinone or .beta.-isorhodomycinone into the antibiotics (I), in the presence of .alpha.-citromycinone or .beta.-isorhodomycinone in a pertinent nutrient medium.