Objectives: The study aimed to investigate sex differences associated with sleep duration and the prevalence of thyroid disease among South Korean adults.Methods: This cross-sectional study included 17,555 adults who participated in the Korea National Health and Nutrition Examination Survey from 2016 to 2018. Sleep duration was categorized into three groups (insufficient, <7 hour; normal, 7-8 hour; prolonged, ≥9 hour). A chi-squared test was performed to assess baseline characteristics. Multiple logistic regression analysis was used to identify the association between general characteristic and the prevalence of thyroid disease. In subgroup analysis, multiple logistic regression analysis was performed to find the association between sleep duration and prevalence of thyroid disease by sex.Results: For men, insufficient and prolonged sleep durations were increased risk of thyroid disease compared with normal sleep duration (insufficient sleep: odds ratio, OR=1.85, 95% confidence interval, CI=1.19-2.87; prolonged sleep: OR=1.71, 95% CI=1.02-2.87).Conclusions: This study found that men with insufficient and prolonged sleep were associated with thyroid disease. Further studies are needed to identify the relationship between sleep duration, thyroid disease, and sleep quality by sex.