A diaphragm portion 20 causes deflection, when high-temperature fluid pressure acts on the pressure sensing surface A of the diaphragm portion 20. This deflection is transmitted via pressure transmitting members 7, 8 to a deflection sensing member 6 which generates an electric signal in response to a pressure received.The diaphragm portion 20 has a recess portion 21 at its center. The recess portion 21 is symmetrical about a central axis of the diaphragm portion 20. A tip end of the pressure transmitting member 7 is brought into contact with the recess portion 21 at a central point. A tapered portion 2d of the diaphragm 20 has a thickness of t.sub.3 which is not larger than the thickness t.sub.1 of an outer peripheral portion 2b or t.sub.2 of a central bottom portion 2c. Furthermore, a heat insulating plate can be provided on the diaphragm to protect the surface A of the diaphragm portion from heat radiation of high-temperature fluid.