PURPOSE: To detect a noise only with precision by inputting the noise generated by a diode to an antenna temporarily by electrostatic coupling.

CONSTITUTION: A noise detecting circuit consists of a diode 1 to be detected, a flyback transformer 2, a transformer driving circuit 3, a reference source 6 for determining a noise detection level, a comparing circuit 7, an AND circuit 8, a gate circuit 9, a load 10, a television set 11 and its antenna 12, and an electrostatic coupling circuit 13 for inputting a current flowing through said diode 1 to the antenna 12. The transformer driving circuit 3 drives the flyback transformer 2, and consequently a high voltage is applied to the diode 1 to be detected to flow a current through a load 10. This current signal is inputted through the electrostatic coupling circuit 13 to the antenna 12, and the television set 11 receives it to output a video signal. The video signal is compared by the comparing circuit 7 with the output voltage of the reference power source 6 and the output is supplied to the AND circuit 8.