Disclosed is a motor driving apparatus in which provisions are made so as to easily isolate the cause of a fault in the event of the occurrence thereof. The voltage and current in each phase of the AC power being supplied to a converter are detected, and the most recently detected data are stored in a power supply monitoring unit for a predetermined period of time. If an alarm occurs in the converter, inverter, or controller, the data currently held in the power supply monitoring unit are recorded in a recording unit. By displaying the thus recorded data, one can easily identify whether the cause of the alarm is due to the power supply or the motor driving apparatus itself.