Abstract: A capacitance detector for detecting a capacitance variation from a video disk and demodulating the capacitance variation into an electric signal, comprises a first block which includes a fixed oscillator, and a coupling loop comprised of a coupling coil and a coupling capacitor, the inductance of the fixed oscillator being inductively coupled with the coupling loop; and a second block which includes a disk stylus resonator having its resonance frequency varied by the capacitance variation of the video disk. A shield plate separates the first block from the second block and a coupling window is provided which inductively couples the coupling loop with the resonant inductance of the disk stylus resonator.