PURPOSE: To provide a differential pressure measuring device simple and low- priced with high excessive pressure detecting reliability by computing the difference of both signals of distortion detecting elements disposed respectively at the edge part and in the vicinity of the center part of a diaphragm.

CONSTITUTION: The high pressure side measuring pressure and the low pressure side measuring pressure are respectively applied to measuring chambers 21, 26 provided on both sides of a diaphragm 23. The diaphragm 23 is distorted according to the pressure difference between the high pressure side and the low pressure side, and this distortion quantity is electrically detected by distortion detecting elements 61, 62 to measure differential pressure. In the case of excessive pressure being applied to the diaphragm 23, the diaphragm 23 is backed up by the wall of either one of the chambers 21, 26. At this time, the difference of detected distortion between a distortion detecting element 62 disposed being slightly shifted from the center of the diaphragm 23 and a distortion detecting element 61 disposed at the edge part of the diaphragm 23 is computed. The excessive pressure can be thereby judged with high reliability.