Provided are an organic-light-emitting-diode (OLED) flat-panel light-source apparatus and a method of manufacturing the same. The device includes an anode and a cathode, to which externally applied power is supplied, disposed on a substrate, an organic emission layer (EML) interposed between the anode and the cathode and configured to emit light due to power supplied through the anode and the cathode, and a subsidiary electrode layer including a plurality of subsidiary electrodes bonded to the anode or the cathode and configured to supply power to the anode or the cathode or electrically insulated from the anode or the cathode and configured to supply power to other emission regions.