The discharge lamp lighting device for supplying alternating current to a discharge lamp includes: a power supply control part having a segment signal generation part, a peak value control part, and a frequency control part; and a power supply part. The peak value control part sets a specific segment period, which indicates a value where a value of integral corresponding to a product of the length of the segment period and a peak value set in a segment period is most deviated from an average value of the values of integral within the specific period, to a period other than a final segment period positioned at the final end of the specific period, among a plurality of segment periods belonging to the specific period.