Radiation therapy (RT) is one of the managements for unresectable hepatocellular carcinoma (HCC). Traditionally, RT has played only a limited role in HCC treatment because of its low efficacy and the low tolerance of the liver for this modality. However, as the technology of RT grows rapidly in recent years, indication of RT for HCC has been extended remarkably. Stereotactic body radiation therapy (SBRT) is a technique that allows precise delivery of a large ablative radiation dose to the tumor while sparing normal surrounding tissue in 1 to 5 fractions. As RT becomes useful therapeutic strategy, the important problem is that there could be serious complication after RT. Here we present a case of 54 years old male with advanced stage of HCC, who underwent a serious neurologic complication of paraplegia following Cyberknife (CK) treatment. He had a huge HCC in right lobe of the liver, and initially transarterial chemoembolization (TACE) was performed with an unsatisfactory response. Therefore, CK was performed, and another TACE was done for a new lesion, which was followed by remarkable complete remission of the tumor. However, paraplegia developed in both of his lower extremities a year after CK. Investigation has shown radiation myelitis as the cause of paralysis. Three and a half years have passed since CK treatment, and HCC is still in complete remission state, however, paraplegia is persistent now. Radiation myelitis should be considered as a complication, when CK is applied to treatment of HCC.