Traumatic brain injury patients have been increasing due to various accidents. After acute therapeutic intervention, rehabilitation is the conventional main treatment with medication. However, in chronic stage, there seems to be some limitation in obtaining functional improvement in spite of comprehensive rehabilitation. Cell therapy like Umbilical cord blood (UCB) transplantation has showed promising results in many animal studies. The mechanism of such neurological improvement is not fully understood. Stem cells included in UCB are expected to secrete neurotrophic factors to enhance brain function. In addition, anti-inflammatory effects of UCB are suggested. Autologous UCB are not available in most of the cases in fact. The aim of this clinical trial is to determine the safety and efficacy of allogeneic UCB.