PURPOSE: To raise a sampling frequency without lowering the amplification degree of the signal cycle to enhance the detection accuracy in a physical quantity detection device wherein a physical quantity is converted to variation of a cycle of a pulse signal and the cycle is amplified to be converted to digital data.

CONSTITUTION: A physical quantity device is disclosed herein. Pulse signals CKB, CKA each having a frequency varying in accordance with an ambient magnetic intensity are outputted from oscillators 16, 18, respectively. The cycles of the pulse signals CKB, CKA are respectively amplified by means of counters 20, 22 and decoders 24, 26 to be inputted to a pulse phase difference coding circuit 30. The phase difference is converted to digital data DAB. An interpolation circuit 40 interpolates digital data DAB to output digital data DD by taking the pulse signal CKB from the oscillator 16 as a sampling signal. As a result, the digital data DAB is interpolated without providing a specific oscillator to the interpolation circuit 40, thereby accurately detecting the magnetic intensity.