Heart sound occurs when the heart contracts and expands. It provides information on myocardial contractility and blood vessels, which is not obtainable from ECG. For this reason, stethoscopy of heart sound in anesthesiology is a very crucial means for acquiring cardiac information and preventing intraoperative medical accidents, and it requires a system for precise objective measurement and analysis of heart sound and murmur. Thus, this study purposed to develop portable digital esophageal stethoscope (PDES) that can objectify and quantify heart sound and murmur. In this study, we designed PDES for precise measurement and analysis of heart sound and murmur data. Heart sound information obtained by inserting the sensor of the PDES into the patient's esophagus can be transmitted to a terminal or a PC and displayed on the screen The amplitude and waveform of heart sound are displayed using self-developed software Heart Sound 1.0. The results of experiment with the developed PDES showed that data on the amplitude and waveform of heart sound and murmur were produced stably in real-time. In addition, when heart sound was heard using a headphone, the sound was clear without external murmur. The PDES developed in this study, which complements the disadvantages of traditional esophageal stethoscope while preserving its advantages, could not only examine heart sound and murmur using an esophageal catheter but also display the amplitude and waveform of heart sound and murmur and measure the patient's body temperature. Accordingly, the developed PDES is expected to be useful in the continuous stethoscopy of heart sound during operation and to contribute to research on heart sound by providing heart sound data.