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 of the piezoelectric substrate 11 and defines a cavity hermetically sealed between the piezoelectric substrate 11 and the sealing substrate; an IDT (Inter Digital Transducer) 16 that is formed on one surface of the piezoelectric substrate 11 and is arranged inside the cavity; and external connection electrodes 18 that are formed on at least one of the piezoelectric substrate 11 and the sealing substrate 12, exposed to an outside of the package 13, and conducted to the IDT 16 through extraction electrodes. In the piezoelectric substrate 11, the other surface is formed with a recess that exposes the inside thereto, and a thin portion positioned in a bottom surface of the recess is a displacement part 21 that is displaced according to a dynamic quantity affected from the outside of the package.