To provide a pressure detecting device which utilizes magnetism and has a stable temperature characteristic.

A pressure detecting device is provided with a magnetism sensitive body which outputs the signal corresponding to magnetism, a housing 1 on which the magnetism sensitive body is placed, a diaphragm 2 which is attached to the housing 1 so as to shield the magnetism sensitive body from the outside, and a permanent magnet 5 which is confronted with the magnetism sensitive body on the inside of the diaphragm 2 and the materials constituting the diaphragm 2 and housing 1 contain ferromagnetic materials. Therefore, the pressure detecting device is constituted so that the magnetism sensitive body and magnet 5 can be surrounded roughly by the ferromagnetic materials.