The present invention relates to a circuit failure detector comprising: an input terminal for receiving a detection signal having a first frequency from an interlock circuit; a correction circuit for correcting the voltage of the received detection signal; a first comparator comparing the corrected detection signal with a first reference voltage and outputting a high voltage signal or a low voltage signal; a second comparator inverting the corrected detection signal, comparing the inverted detection signal with a second reference voltage, and outputting the high voltage signal or the low voltage signal; a counting signal generator for generating a counting signal having a second frequency; a first coupler for coupling an output signal of the first comparator with the counting signal; a second coupler for coupling the output signal of the second comparator with the counting signal; and a controller for detecting a circuit failure on the basis of the output signal of the first coupler and the output signal of the second coupler.