Devices to measure the blood pressure of patients are being used without any calibration in a hospital. It is an important to show consistent values when any medical devices measure the same patients regardless they are sphygmomanometer or fully automatic electronic blood pressure meter. We compared sphygmomanometer and fully automatic electronic blood pressure meters with standard digital blood pressure monitor (SDBPM) to evaluate the consistency of the small healthy subjects. We measured the blood pressure from six healthy subjects (three of 20~40 years and three of 40~60 years old). Two sphygmomanometer and two fully automatic electronic blood pressure meters were used and compared with the SDBPM. Blood pressures measured from right and left arms each and were compared. All six healthy subjects showed normal blood pressure values. In general, left blood pressure values showed higher values than right side. Comparing SDBPM, with the other monitors, the systolic pressure showed ${pm}$ 34.8% difference and ${pm}$ 33.3% for the diastolic pressure. Correlation between SDBPM and Sphygmomanometer was 0.59~0.71, and 0.50~0.70 for fully automated digital BP monitors. It fell in grade-D when we apply the BHS(British hypertension society). AAMI(American association for the advancement of medical instrumentation) also showed unsatisfactory results for the mean value (${leq}$ 5 mmHg) and standard deviation (${leq}$ 8 mmHg). We tested sphygmomanometer and fully automatic electronic blood pressure meters and compared with a standard digital blood pressure monitor. All devices showed inconsistent blood pressures. A reliable calibration system is highly needed for all devices in all hospitals.