To provide a structure capable of reducing or eliminating the surface tensions of enclosed liquids by providing voids in between the rear surfaces of overpressure-protected diaphragms and the surfaces of contact liquids.

This differential pressure transmitter has a high pressure side liquid contacting means comprising a high pressure side process diaphragm for transmitting high pressure from a process to an enclosed liquid and a high pressure side overpressure-protected diaphragm, a low pressure side liquid contacting means comprising a low pressure side process diaphragm for transmitting low pressure from the process to an enclosed liquid and a low pressure side overpressure-protected diaphragm, and a differential pressure sensor for sensing the difference in pressure between the high and low pressure side enclosed liquids. Voids are provided in between the rear surfaces of the high pressure and low pressure side overpressure-protected diaphragms constituting means for contacting the high pressure and low pressure side liquids and the high pressure and low pressure contact liquid surfaces, whereby the contact areas are reduced when contacts occur on the high pressure and low pressure liquids surfaces.