To provide a sensor that is capable of improving signal strength and detection sensitivity of SAW (Surface Acoustic Waves) and ensuring high operation reliability over a long period of time, and in which manufacturing facilitation and cost reduction are easily achieved with a simple structure.

A sensor 10 is provided that comprises: a package 13 including a piezoelectric substrate 11 and a sealing substrate 12 that is jointed to one surface 11a of the piezoelectric substrate and defines a cavity hermetically sealed between the piezoelectric substrate and the sealing substrate; an IDT (Inter Digital Transducer) 16 that is formed on one surface of the piezoelectric substrate and is arranged inside the cavity; and external connection electrodes 18 that are formed on at least one of the both substrates, exposed to an outside of the package, and conducted to the IDT through extraction electrodes. The piezoelectric substrate has a displacement part 21 that is displaced according to a dynamic quantity affected from the outside of the package, and is provided with an opening part E that allows the displacement part to be exposed to the other surface side of the piezoelectric substrate.