A discharge lamp ballast having a starting circuit including a second inductor connected between a first end of a discharge lamp and the positive voltage side of a first capacitor; a second capacitor forming a resonance circuit together with the second inductor; a second switching element connected between the positive terminal of a DC power source and the second end of the lamp; a third switching element connected between the second end of the lamp and the negative voltage side of the first capacitor; and a starting controller that controls both switching elements. The starting controller alternately turns both switching elements on and off so as to contribute resonance voltage of the resonance circuit for starting of the lamp in case of the starting mode.