The utility model provides a cubical switchboard fault detection device, includes filtered light sensor, signal processing unit, industrial computer, and filtered light sensor connects signal processing unit, and signal processing unit connects the circuit breaker of industrial computer, signal processing unit linked switch cabinet. Filtered light sensor's output pulse electric current signal transfer gives signal processing unit, and signal processing unit is used for switch cabinet control's circuit breaker action. The industrial computer is used for the arc light of the same wavelength of analysis department strong and weak, confirms cubical switchboard fault type. The industrial computer is used for the different filtered light sensor output pulse signals of analysis strong and weak, carries out fault locating. Filtered light sensor is a plurality of, and a plurality of filtered light sensor install at the cubical switchboard inner wall. The utility model relates to a cubical switchboard fault detection device, the arc light of the same wavelength of analysis department is strong and weak confirms the cubical switchboard trouble, has sensitivity, accuracy, quick, advantage such as the selectivity is good.