Atrial fibrillation is the result of the atria pacing themselves without listening to the command of the sinus node, the commander-in-chief. Unlike premature beats, atrial fibrillation is an irregular beating of the atria that causes the heart rate to be absolutely uneven and the pulse rate to be irregular and less than the heart rate. Atrial fibrillation itself is not frightening, and some people do not feel anything even when they are in atrial fibrillation, but if the ventricular rate in atrial fibrillation is greater than 100 beats per minute or if there is a risk of embolism, it must be prevented before it happens. These two points are also fundamental to the need for treatment of atrial fibrillation. There are many causes of atrial fibrillation, including hypertension, rheumatic heart valve disease, cardiomyopathy, cardiac insufficiency, hyperthyroidism, and of course, isolated atrial fibrillation without any cause. Different causes have different consequences and different treatment methods. Therefore, it is recommended to actively search for the cause of atrial fibrillation when it is detected, and to treat both symptoms and causes so that atrial fibrillation can be treated most appropriately.