A hemadynamometer is provided. The hemadynamometer includes a bag, an inflation unit, a deflation unit, a piezoelectric device and a processor. The bag is used for wounding on the user's wrist or upper arm. The inflation unit is used for inflating the pressure inside the bag, and the deflation unit is used for deflating the pressure inside the bag. When the blood in the artery of the user oppresses the piezoelectric device, the piezoelectric device outputs a number of pulse piezoelectric signals accordingly. The processor is used for comparing the waveform slope of the pulse piezoelectric signals to determine a systolic blood pressure value and a diastolic blood pressure value.