The present invention provides an amplitude modulator, which is disposed in an area through which a magnetic field flows so as to modulate amplitudes, comprising: a substrate; a first driving electrode which receives a first frequency signal and a second frequency signal supplied from the substrate and carries out resonant motion by the magnetic field; and a second driving electrode for receiving the second frequency signal and carries out resonant motion by the first driving electrode and the magnetic field, wherein a modulated signal is generated by modulating the amplitudes of the first and second frequency signals through the resonant motions of the first and second driving electrodes. Therefore, since the signal generated by modulating a carrier signal through mechanical resonance according to the magnetic field is outputted, amplitude modulation can be carried out without a complicated circuit configuration. In addition, since an MEMS device is a single structure that does not include an insulating layer, a single signal is applied to one structure, thereby simplifying driving, and all the driving electrodes of both ends thereof are driven so as to double a change in variable capacitance, thereby improving sensing ability.