Disclosed is a device for detecting an instantaneous maximum output current of an inverting module as a peak-current thereof. The inverting module converts a direct current (DC) link voltage to an alternate current (AC) voltage, and includes three-phases legs. Each leg has lower and upper switching elements connected in series. The device includes a shunt resistor serially connected to a lower switching element of each leg of the inverting module; a current detection module configured for detecting an output current from a signal output from each shunt resistor; and a summer configured for receiving and summing the detected output currents from the current detection module and outputting the instantaneous maximum output current of the inverting module as the peak-current thereof.