Background Socioeconomic status (SES) differences could influence management and clinical outcomes in patients with atrial fibrillation (AF), reflecting health inequalities. The authors aimed to investigate emergency department (ED) visits in patients with AF according to SES level. Methods and Results The authors performed a cross-sectional analysis of ED visits in patients with nonvalvular AF using the Korean National Health Insurance Service database in 2016. The patients were divided into health premium quartiles and medical aid groups, with quartile 4 the highest SES and medical aid the lowest SES. Among patients with AF, patients who had ≥1 ED visits in 2016 were identified. The prevalence and cause of ED visits, 30- and 90-day mortality, and rehospitalization risk after ED visits were evaluated. Among the total 371 017 AF patients, 99 306 patients visited the ED in 2016. The medical aid group showed the highest ED visit rate (n=11 833, 38.0%), and patients with the highest quartile of SES (quartile 4 group) showed the lowest ED visit rate (n=38 037, 30.0%). The most common cause of ED visits was cerebral infarction in all groups. The 30- and 90-day mortality rates and rehospitalization risk after ED visits was higher in groups with lower SES. Conclusions Patients with AF and with lower SES had a higher risk of ED visit rate, higher 30- and 90-day mortality rates, and rehospitalization risk after ED visit. Tailored AF management according to different SES levels in patients with AF is needed to improve clinical outcomes.