Text book in all medical school showed that the baroreflex system is one of the most important regulatory systems. When blood pressure increases, heart rate decrease and an artery is dilated with the baroreflex system. By decrease of cardiac output and arterial resistances, blood pressure returns to the normal value. However, there is no diagnostic method, which can measure the sensitivity of a baroreflex system of the artery by the simple methodology. We had challenged invention of the new machine, which could diagnose the sensitivity of the baroreflex system of not only a heart, but also an artery. In this system, the measurement sections are only an electrocardiography (ECG) and peripheral pulse wave. These time series is inputted into a personal computer system, and analyzed quantitatively. Responses of the artery were measured with pulse wave velocity (PWV) calculated from pulse wave transmission time from heart to an artery. In this system, the heart rate change corresponding to the blood-pressure change in time series sequence is observed. Delay time was measured by the cross correlation function. Slope of the blood pressure (BP) change and heart rate (HR) change showed the sensitivity of the baroreflex system of heart. Furthermore, this system can measure the sensitivity of the baroreflex system of an artery. Change of PWV in response to the BP change was observed. We found that significant correlation was observed in the time sequence between BP change and PWV change after delay time calculated from cross correlation. Clinical research was started through allowance of the Ethics Committee. Decreased sensibility in the hypertensive patient's baroreflex system was observed as a result of the clinical research. Furthermore, alteration of the baroreflex sensitivity before and after the drug administration was evaluated. For example, Azelnidipine, Calcium antagonists improved the baroreflex sensitivity of the artery in several cases. This system may be useful for the follow up of the hypertensive patients.