PURPOSE: To obtain a differential type pressure sensor which can be handled easily and is not affected by external force and noise for measurincj the pressure difference between two points and the alternate frequency.

CONSTITUTION: A piezoelectric ceramic plate 19 is adhered to a diaphragm 16. The inside of a sensor case 20 where the diaphragm 16 is mounted to an opening is subdivided into two cavities 25a and 25b by the diaphragm 16 and a first screening plate 22a which is adhered to the surface inside the sensor case 20. Conduits 23 and 24 for leading the pressure at a part where a pressure difference is measured to each cavity in the sensor case 20 are mounted to the sensor case 20. The front surface of the case 20 is provided with a second screening plate 22b located on the extension of the first screening plate 22a and is covered with a cover 33 for dividing the front space of the diaphragm 16 into the cavities 25c and 25d.