PURPOSE:To digitally display measured pressures and make reading of scale accurate and easy by floating a magnet on the mercury in a mercury gauge and fetching out the up and down movements of the magnet owing to the up and down movements of the mercury column as electrical changes. CONSTITUTION:A magnet 14 is floated on the mercury 13 in a mercury gauge 12 and the movements of the magnet 14 moving up and down according to the up and down of the mercury 13 are detected by a detecting part 16 from the outside. The detection outputs thereof are sent to a dispaly control part 21 through a conversion part 17, amplifier part 18, A/D converter 19 and pressure counter part 20. On the other hand, Korotkov signals are sent out to the microphone 22 in the arm band and are inputted to the display control part 21 through an amplifier part 23, filter 24 and Korotov sound discrimination part 25. These are also inputted to the display control part 21 from the Korotkov sound discrminating part 25 through a pulse counter part 21, the maximum and minimum blood pressure values and pulse rates are digitally displayed in a display part 27.