Background and Objectives: The aim of this study was to investigate the outcomes and clinical impacts of Maze operation in patients with atrial fibrillation (AF) who underwent valve surgery. Methods: Among 280 patients who underwent valve surgery, 112 patients with AF were enrolled and divided into two groups: group I (Maze group: 56 patients, 52.8짹9.7 years old, 33 females), group II (non-Maze group: 56 patients, 52.9짹10.8 years old, 37 females). Clinical, echocardiographic, and electrocardiographic variables were analyzed between the groups. Results: Sinus rhythm (SR) was maintained in 40 patients (71.4%) during hospitalization and 42 patients (75%) during follow-up period in out-patients clinic. Baseline echocardiographic variables including chamber size, valve area, pressure gradients, and left ventricular ejection fraction (LVEF) were not different between the groups. Post-operative EF (58.9짹10.3 vs 53.7짹12.9 mm, p=0.041) was significantly higher and left atrial (LA) size (40.9짹8.9 vs 46.9짹10.3 mm, p=0.037) was significantly smaller in group I than in group II. However, only LA size was significantly smaller in group I than in group II (50.1짹10.4 vs 42.9짹6.5 mm, p=0.001). In-hospital events or follow-up clinical events were not different between the groups. LVEF was significantly higher and LA size was significantly smaller in patients with SR than in patients with AF within group I during clinical follow-up (LVEF: 61.9짹9.2% in SR vs 55.6짹9.8% in AF, p=0.039, LA size: 42.5짹6.8mm in SR vs 48.0짹6.8mm in AF, p=0.016). Conclusion: Our study demonstrated that Maze operation was an effective method for the conversion of AF to SR and maintenance of sinus rhythm exerted favorable influence on post-operative LV function and LA size in patients who underwent valve surgery.