Abstract: A multi-quality electric power supply apparatus supplies electric power based on the demand of various loads. The multi-quality electric power supply apparatus includes an inverter having a three-phase bridge configuration with an A/C output terminal connected to a distribution line of each phase of the three-phase four-wire A/C system. A capacitor is connected among two input terminals of the D/C side of the inverter and a neutral line of the three-phase four-wire A/C system. An uninterruptable power supply device is inserted from a node point to the distribution line of the inverter in a given distribution line of one phase on the load side to compensate for a voltage drop of the distribution line and to supply a given voltage in the distribution line during an interrupted power supply.