To provide a diaphragm barometer in which, in order to fundamentally solve a problem of temporal change of a standard atmospheric pressure including vacuum of a standard pressure chamber in the diaphragm barometer, the standard atmospheric pressure in the standard pressure chamber is measured even if the atmospheric pressure in the standard pressure chamber in the diaphragm barometer is fluctuated due to temporal change or the like, and the standard atmospheric pressure can be corrected.

A diaphragm barometer having a standard pressure chamber includes a thermal barometric pressure sensor in the standard pressure chamber. An atmospheric pressure in the standard pressure chamber is measured constantly or on demand, and the measured atmospheric pressure is made to be used as a standard atmospheric pressure. A silicon substrate is used as a heat conduction type sensor, and an absolute temperature sensor is provided. The atmospheric pressure in the standard pressure chamber can be adjusted in the vicinity of a desired atmospheric pressure.