Carbonization of bio-dried sludge was conducted under different carbonization condition, and element analysis of sludge char was carried out. In this study, behavior of elements from bio-dried sludge to char during carbonization was revealed. In the experiment, lab-scale bath type reactor was used. In the lab-scale experiment, carbonization of bio-dried sludge was conducted in nitrogen or steam flow circumstance, and carbonization temperature and duration was changed. Elements of sludge char were analyzed after carbonization. The yield of carbon, hydrogen and nitrogen in bio-dried sludge decreased, as increasing carbonization temperature and extending duration. When carbonization duration was extended, yield of carbon and nitrogen decreased in the case of at low temperature. The yield of sulfur in bio-dried sludge decreased slowly against carbonization temperature, but it increased at high temperature over 973 K. Sulfur in bio-dried sludge was remained in sludge char not being decomposed. However sulfur content decreased at high temperature when steam was introduced during carbonization of bio-dried sludge.