A physical quantity sensor includes a deformable body in which strain occurs in response to a stress applied thereto, a vibrator vibrating with a frequency according to the strain or with an amplitude according to the strain, and a processor processing a signal output from the vibrator. The vibrator is mounted to the deformable body such that the strain transmits to the vibrator. The processor is bonded to the deformable body such that the strain does not substantially transmit to the processor. This physical quantity sensor can stably detects strain and tension acting on an object.