This study is to find the optimum classifier that can be easy and robust diagnostic method of the obstructive sleep apnea (OSA) using a heartbeat signal. The heartbeat signal was acquired from the 92 patients with OSA. The dataset consists 98,060 epochs, from them the training sets contained 68,642 epochs from the 63 OSA patients and test sets contained 29,418 epochs from the 29 OSA patients, respectively. The heartbeat signal was analyzed in the time and frequency domain and six features were extracted (normal-to-normal [NN], standard deviation of mean NN [SDNN], root mean square of successive differences [rMSSD], low-frequency [LF], high-frequency [HF], and LF/HF ratio). All extracted features were used to train the following classifiers: linear discriminant analysis (LDA), decision tree (DT), logistic regression (LR), k-nearest neighbor (KNN) and support vector machine (SVM). The top three classifiers (SVM, DT, and LDA) showed the accuracy of 93.2%, 93.2%, and 93.2% for test sets, respectively. Then, the top three classifiers could be effective on sleep studies and OSA detections.