The quenching of ultraviolet-stimulated fluorescence by voltage application in organic solutions of europium benzoyl-trifluoroacetonate are investigated using sandwich-type cells with transparent insulating films of SiO2, SiO, or ZnS. Four types of fluorescent cells are prepared by taking into consideration the relationship among the direction of UV irradiation, arrangement of the electrode coated with insulating films, and the polarity of the applied voltage. It is seen that electric charge transfer between the electrode and the rare earth ions does not take place at the electrode coated with insulating films, where the fluorescent Eu (III) cannot be reduced to nonfluorescent Eu(II). The serious deterioration in the fluorescent properties that is observed at the time of application of the recovering voltage can, therefore, be improved by using a counter electrode with insulating films. Red fluorescence can be switched by alternately applying the quenching voltage and the recovering voltage across the cells.