In this paper, we propose a personal authentication method using heartbeat waveforms to enhance the security in wireless communication. In the heartbeat waveforms of a human being, it is known that there are discriminative characteristic features and the mimicking is very difficult. Therefore, their application to personal authentication has been studied. Existing method performs personal authentication using a chaos indicator of ECG. In this paper, we propose an authentication method that extends the index in order to increase the accuracy of authentication. To validate that our personal authentication method is applicable, we perform some experiments to show that our method provides better authentication than existing one.