Rb4Ta6O17 with a layered structure showed ultraviolet emission around 340 nm by photoexcitation at 270 nm. The ultraviolet emission was observed even at room temperature. The luminescent properties of Rb4Ta6O17 were compared with those of K4Nb6O17 with the similar layered structure and other tantalates. The Stokes shift was smaller than that of other tantalate phosphors. The excitation energy in Rb4Ta6O17 was delocalized more or less.