Objectives: In South Korea, a significant number of patients with obstructive sleep apnea have benefited from the insured continuous positive pressure for sleep apnea as of 2018. However, there is limited information on public awareness of sleep apnea syndrome in the country. A nationwide survey was conducted to evaluate the current status of public awareness on the diagnosis and treatment of sleep apnea. Methods: We conducted an online survey using structured questionnaires on symptoms and knowledge of diagnosis and treatment modalities for sleep apnea. A total of 4,000 participants aged 21 to 69 were proportionally allocated according to the residential area, gender, and age group. Results: The STOP questionnaire, a screening tool for sleep apnea, revealed that 1,044 (21.6%) scored ≥2 points, 327 (8.1%) scored ≥3 points, and 64 (1.6%) scored 4 points. However, only 19 of the 1,044 patients were being treated for sleep apnea, and 13 had been using continuous positive airway pressure. For the diagnosis of sleep apnea, 1,318 participants (33.0%) responded that polysomnography was necessary. For sleep apnea treatment, 1,954 (48.9%) participants responded that lifestyle modification was the treatment of choice, while 1,036 (25.9%) chose continuous positive pressure. Conclusions: Although one-fifth were at high risk for sleep apnea, this disorder is still underestimated. Therefore, publicity and support are needed to improve public awareness of sleep apnea.