The present invention discloses an arc-discharge detection device, which is used to detect the arc discharge persistently occurring in between an inverter and a load during an abnormal power transmission state. The inverter is arranged in a circuit board, and a carbonized loop is defined in an arc-discharge reaction area of the circuit board. In the present invention, a power-variation detection unit is electrically coupled to the carbonized loop and detects the power-level variation caused by the carbonized loop and generates a power-variation signal; an interpretation unit receives the power-variation signal and utilizes a decision level to determine whether the power variation is caused by arc discharge and outputs an abnormal-power signal if the interpretation result is positive; and a trigger unit is driven by the abnormal-power signal to interrupt the inverter's outputting high-voltage power to the load.