PURPOSE: To obtain a diaphragm Bourdon pressure gauge which causes a few troubles while used and can easily be repaired in case of a trouble, by using as a diaphragm a tubelike sheet provided to a duct.

CONSTITUTION: Tubelike sheet 5 of natural or synthetic elastic resin is fitted direct to the duct to the duct of Bourdon-tube 1 by a flange. Parts S and S' are filled with a sealing liquid. This constitution eliminates completely a dead space of a diaphragm pressure gauge and solves troubles due to blocking, sticking, etc. Further, no special technique is needed to supply or change the sealing liquid and at the normal pressure, the supply and change can be done through simple operation. Further, a protective flange of Teflon, etc., as sheet 5 is worked by glass-lining and Teflon-lining to increase corrosion resistance, and air in tube 1 is buffered against pulsating pressure at a pump outlet, so that the abrasion lifetime can be prolonged.