This study was carried out to develop a new sweet sorghum for biomass by using mutagen, gamma-ray. Seeds treated were gained from National Genetic Resource Center, RDA, and these seeds were irradiated with gamma-ray (400Gy) at KAERI. CNUS-M113 and CNUS-M134 among 169 collected accessions were evaluated a promising line for biomass due to increasing of fresh and dry weight. In addition, this line was high in stem height, number of tiller and fresh weight per plant than check, Hwang-gum chal sorghum. Accordingly, this line demanded for leading variety the production test and cultivation adaptability in future years.