In this clinical trial, Rivaroxaban of standard dose (20mg) and reduced dose (15mg) will be administeted in non-valvular atrial fibrillation patients without severe renal dysfunction. It is a randomized, open-label, and phase 4 clinical trial to compare and evaluate efficacy and safety of Rivaroxaban. After obtaining informed consent to participate in this trial, screening is performed (Screening visit). Screening includes baseline 12-lead electrocardiography and laboratory tests to exclude severe end-organ dysfunction (such as renal dysfunction, liver dysfunction, or anemia). Baseline visits are available on the same day. After screening, subjects eligible for the trial will be randomly assigned (1:1 ratio) to Group 1 (15 mg of Rivaroxaban) or Group 2 (20 mg of Rivaroxaban) (Baseline visit). The study drug (Rivaroxaban 15mg or 20mg daily) will be administered for 12 months. During study period, a total of six visits (3,6,9,12 months) will be made, and follow-up test and outcome measurement will be done in each visit.