A semiconductor differential pressure sensor includes a pressure detection element, which is arranged such that its main surface is fixed on a top of a first protrusion with an adhesive while a second protrusion is fitted into its opening. Thus, the pressure detection element is held with high holding power at an exact position. Moreover, the adhesive does not flow into a first pressure introducing path, whereby blocking of the first pressure introducing path is prevented. Furthermore, by providing a recess around the first protrusion, influence of thermal deformation of a resin package on pressure detection characteristics is decreased.