PURPOSE: To secure high accuracy without compensation or calibration and to simplify the structure, by connecting two diaphragm having different effective areas, simultaneously applying the pressure, detecting the displacement, generating a repelling force in the direction for offsetting the displacement by an electromagnetic force generating part, and measuring the pressure based on an exciting current at the time.

CONSTITUTION: When the pressure of fluid to be measured is simultaneously applied to the diaphragm 11 and 12 through a connecting port 26, the diaphragm 12 having a large area is forcibly pushed owing to the difference in the effective areas, and a connecting rod 13 is tend to move to the side of the diaphragm 11. Therefore, the displacement is detected by a displacement detecting part 18, and the detected signal is sent to an amplifier 22. The output of the amplifier 22 is given to an electromagnetic coil 21b. The repelling force to the diaphragm 12 is generated in a permanent magnet 21a so as to offset the displacement of the connecting rod 13. The exciting current at this time is read by an ammeter in a reading part 24, and the pressure of the fluid to be measured is determined.