<p>Provided is a discharge lamp lighting device, whereby it becomes possible to prevent or suppress the occurrence of flickering during the lighting of a discharge lamp by a second lighting mode in which a lower alternate current electric power than a rated electric power is fed when the switching from a first lighting mode in which an alternate current electric power that is the rated electric power is fed into the second lighting mode is carried out. A discharge lamp lighting device comprises a discharge lamp which has a pair of tungsten-made electrodes each having a protrusion formed at the tip thereof and an electric power feeding device which feeds an alternate current electric power to the discharge lamp, and is characterized in that the power feeding device has a function of switching between a first lighting mode in which a rated electric power is fed to the discharge lamp and a second lighting mode in which a lower electric power than the rated electric power is fed to the discharge lamp to light the discharge lamp and, therefore, can control an electric power to be fed to the discharge lamp under such conditions that the average electric power change rate becomes 0.01-2.1 W/s during a mode switching period in which the switching from the first lighting mode into the second lighting mode is carried out.</p>
