A differential pressure sensor includes a sensor chip provided with a sensor diaphragm, a first retaining member bonded facing a peripheral edge portion of one face of the sensor diaphragm and having a first pressure guiding hole guiding a first fluid pressure to the one face of the sensor diaphragm, and a second retaining member bonded facing a peripheral edge portion of the other face of the sensor diaphragm and having a second pressure guiding hole guiding a second fluid pressure to the other face of the sensor diaphragm. The differential pressure sensor also includes a sensor housing having a sensor chamber containing the sensor chip, a first pressure guiding duct guiding the first fluid pressure to a first inner wall face of the sensor chamber, and a second pressure guiding duct guiding the second fluid pressure to a second inner wall face of the sensor chamber.