Disclosed is an arrhythmia-diagnosing method and device for diagnosing arrhythmias, such as fibrillation or tachycardia. The arrhythmia-diagnosing method includes the following steps: measuring (a) the heart characteristic length, and the (b) frequency and (c) conduction velocity of the cardiac electrical wave and (d) determining the occurrence or absence of an arrhythmia by using the three parameters measured in steps (a) to (c). With this invention, it is possible to predict and diagnose an electrical wave tornado, one of the causes of arrhythmia, by using a non-dimensional parameter, to identify patients at risk of death or brain death due to an arrhythmia and to reduce the mortality of patients suffering from arrhythmias significantly.
