Disclosed is an arrhythmia diagnosing method and device for diagnosing arrhythmia such as fibrillation or tachycardia. The arrhythmia diagnosing method includes the steps of: (a) measuring a heart dimension； (b) measuring a frequency of a cardiac electric wave； (c) measuring a conduction velocity of the cardiac electric wave； and (d) determining occurrence or absence of arrhythmia using the heart dimension, the frequency of the cardiac electric wave and the conduction velocity of the cardiac electric wave measured in steps (a), (b) and (c). With the present invention, it is possible to predict and diagnose an electric wave tornado, one of causes of arrhythmia, through the use of a non-dimensional parameter, to find out patents who may possibly be died of arrhythmia or may possibly come to brain death due to arrhythmia and to significantly reduce the mortality rate of patients who suffer from arrhythmia.
