Disclosed is an automatic feeding system for an underwater fish farm, which includes a marine base facility standing vertically in the sea； an underwater fish farm installed on an outer surface of the marine base facility； a storage tank installed inside the marine base facility to store feed to be supplied to the underwater fish farm； a feed transfer device transferring the feed discharged through an outlet of the storage tank； a feed supply device mixing seawater with the feed transferred by the feed transfer device and supplying the mixture to the underwater fish farm； a controller installed inside the marine base facility to control operations of the feed transfer device and the feed supply device； and an illumination device installed in the underwater fish farm to illuminate an inside of the underwater fish farm.
