Recently, favorable results of minimally invasive spinal surgery have been reported in comparison to the open decompression or fusion surgery. Biportal endoscopic spine surgery (BESS) has several benefits and Indications for BESS are nearly identical to those for general open spinal surgery. However, it remains a challenging procedure even for an experienced endoscopic surgeon. because it takes a a long operation time while early learning period. If the operation time is prolonged, the advantages of endoscopic surgery are reduced and the incidence of complications can be increased. Therefore, we will investigate the factors affecting the operation time and how to minimize it before and during operation.