A differential pressure transmitter is an improvement over the drawbacks of conventional apparatuses and provides a differential pressure transmitter which compensates for adverse effects of a static pressure by using a static pressure detecting piezoresistive gauge. The transmitter includes a highly sensitive static pressure sensor with high outputs, and a composite sensor with small crosstalk between the static pressure sensor and a differential pressure sensor. The differential pressure transmitter is constructed of semiconductor sensor substrate and a fixed mount on which the sensor substrate is securely mounted; whereby the differential pressure of a fluid is detected by utilizing the difference in Young's modulus between the sensor substrate and the mount. The sensor substrate is processed on one side or on both sides to make a part of the sensor substrate thinner than the surrounding parts and thereby cause a peak stress due to a static pressure load to occur at the thin part, and a change in resistance of a semiconductor piezoresistive gauge formed at that thin portion is detected.