An illuminating device according to an embodiment of the present invention includes
a dielectric barrier discharge type low pressure discharge lamp 1 composed
of a tubular glass lamp vessel 10, in which mercury and rare gas are enclosed,
a first and a second electrode 21,26, which are made of electrically conductive
layer, are provided on an outer surface of both ends of the tubular glass lamp
vessel 10 and a high frequency power source of a floating output type 81,82,
which supplies a sine wave voltage between the first and the second electrodes
of the dielectric barrier discharge type low pressure discharge lamp 1 having
a neutral point of the sine wave voltage being grounded, and which supplies a frequency
in a range from 40 kHz to 100 kHz.
