PURPOSE: To facilitate the connection with an outside circuit, by constructing a detecting circuit element of a type integrated with a connector, and by integrating this circuit element and a sensor unit together by welding.

CONSTITUTION: Oil entering through an inlet port 21 of a casing 20 enters a through orifice 30 of an orifice plate 24, and thereby an oil pressure is applied to a diaphragm 31 disposed so that it blocks up one end of the through orifice 30. Then an internal stress is generated in the diaphragm 31, and a permeability is reduced by a stress-magnetism effect, whereby the inductance of a magnetic circuit is reduced. This reducution of the inductance is detected by a detecting circuit provided on a substrate 49, and an electric signal is accordance with the oil pressure is outputted through terminals 54. In the sensor thus constructed, the detecting circuit on the substrate 49 fitted with various electronic components is soldered to the lower portions of the terminals 54 projecting downward from the lower side of a connector unit 53. Consequently, the sensor and a connector are integrated together, the connection with an outside circuit is facilitated, leads for outside connection become unnecessary, and thus a fault due to the disconnection of the leads is eliminated. In addition, the sensor unit, the connector unit and the detecting circuit are integrated together, and thus the sensor becomes compact.