Recently, it has been reported that chemical hair coloring can cause allergic reactions, the toxicity issue of chemical hair color was issued. Therefore, there is an increasing interest in the hair coloration technique using non-toxic and bio-compatible hair color gotten from natural resource. In this study, the possibility using fermented Indigo as natural hair coloring agent was investigated. Bleached hair samples were dyed using Indigo, and the effect of dyeing frequency, the physical change after dyeing, color, surface and cross-section characteristics, and tensile property were also studied. In addition, the protection property of cationic detergent finishing on damaged hair samples were also studied. The following conclusions are made; 1. While bleached hair samples with low value showed the negligible effect of repeated dyeing, bleached hair samples with high value showed the good effect of repeated dyeing. 2. Hair sample dyed with Indigo showed a high light-fastness, however, tensile strength and elongation showed very low values (high damage on hair sample). 3. Cationic detergent finishing did not affect on the colorfastness because of decoloration after dyeing, however, it increased the smoothness of hair sample, and therefore, can use as protectant of damaged hair. 4. Hair scale was damaged after dyeing. It seemed that the alkali, potassium carbonate, increased pH of dyeing bath to 11, as a result, the hair was swollen, weaken, and dissolved on the prolonged dyeing time. Dyed hair sample became stiff and fine. 5. The color difference was 4.62 (a high fastness value) in the test of sunlight exposure, shampoo, cationic detergent finishing, and acid perspiration fastness.