There is provided a discharge-lamp lighting device that, upon start-up of a high-intensity discharge lamp, alternately outputs a period A during which a starting circuit applies a high voltage to the high-intensity discharge lamp by resonance operation when a DC/AC inverter outputs a high-frequency voltage, and a period B during which the DC/AC inverter applies a low-frequency-square-wave voltage or a DC voltage to the high-intensity discharge lamp via the starting circuit. The period A for applying the high voltage by the resonance operation is set to about a time enough for a high-intensity discharge lamp in an initial aging stage to cause a dielectric breakdown, and a period C for alternately outputting the high-voltage generating period A and the period B for outputting the low-frequency-square-wave voltage or the DC voltage is set to about a time enough for a high-intensity discharge lamp in a life's last stage to cause a dielectric breakdown.