A new use of dunnione compound, a pharmaceutically acceptable salt thereof, a prodrug thereof, a solvate thereof, or an isomer thereof as an effective ingredient for prevention or alleviation of hair loss is disclosed. The dunnione compound, a pharmaceutically acceptable salt thereof, a prodrug thereof, a solvate thereof, or an isomer thereof, in an animal model, showed an effective reduction of hair thinning as well as an effective reduction in loss of hair follicles and inner root sheaths. Thus, the duunione compound, a pharmaceutically acceptable salt thereof, a prodrug thereof, a solvate thereof, or an isomer thereof can be used effectively to treat hair loss and/or loss of hair follicles and inner root sheaths, promoting hair regrowth. The hair loss may be caused by anticancer therapy.