A lamp assembly includes a lamp and a lamp driving device. The lamp includes a body and first and second electrodes. The body converts invisible ray generated by a discharge into visible ray, and the electrodes are disposed on the body. The lamp driving device provides the first and second electrodes with first and second driving voltages, respectively, to generate the discharge. The first driving voltage is less than a first critical voltage at which a corona discharge occurs at the first and second electrodes. When the first electrode is electrically connected to a ground, the first critical voltage may be about 1,200 volts. When the second driving voltage has an inverted phase with respect to the first driving voltage, the first critical voltage is about 2,400 volts. An ozone gas may not be generated at the first and second electrodes to prevent the damage of the electrodes.