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 C 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 in a joint part of the piezoelectric substrate 11 and the sealing substrate 12 and inside the cavity C; through electrodes 33 that penetrate through the sealing substrate 12 or the piezoelectric substrate 11 in a thickness direction and are conducted to the IDT 16; and external connection electrodes 18 that are formed on at least one of the piezoelectric substrate 11 and the sealing substrate 12 and are conducted to the through electrodes 33. The piezoelectric substrate 11 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 21 to be exposed to the other surface side of the piezoelectric substrate 11.