A pressure measuring apparatus comprising a diaphragm to which pressure to be measured is applied and a resilient vibrator connected to the diaphragm, which acts to produce a signal based on its natural frequency relative to the pressure, wherein the diaphragm comprises a peripheral circumferential portion, a central fixing portion and a non-planar intermediate portion therebetween, with the central portion being connected to the vibrator and having its edge disposed at a non-perpendicular angle with respect to the vibrator area to which it is connected. The apparatus eliminates adverse influences due to initial distortion, hysteresis of the diaphragm and produces accurate measurements.