Obstructive sleep apnea (OSA) is a chronic disease with the risks of secondary cardiovascular or metabolic diseases. Continuous positive airway pressure (CPAP) is the first line treatment for OSA, but patients who fail the treatment with CPAP or other conservative treatment, should be considered for surgery. The early target of sleep surgery was the oropharynx by tonsils, uvula, and soft palate. However, a better understanding of the pathophysiology of OSA and improvement of diagnostic methods has revealed multi-level obstruction in the upper airway. The base of tongue is one of major contributors to OSA and many surgical methods have been developed to resolve the compromise of retroglossal area. Careful examinations of obstruction site and its structured approach to surgery with less morbidity should be evaluated and understood for the better outcome by sleep surgery.