A discharge lamp lighting circuit includes a power supplying portion having a series resonant circuit containing transistors and a bridge driver, and a control portion for generating a control signal Sc1 to control a driving frequency of the bridge driver. The control portion has a sample hold portion for generating a constant control signal S1, a frequency follow-up control portion for generating a control signal S2 in such a manner that a phase difference between a voltage and a current in the series resonant circuit is approximately zero, and a power control portion for generating a control signal S3 in such a manner that a magnitude of an AC power approximates a steady value. The control signal S1 is selected from a time t3 to a time t4, the control signal S2 is selected from the time t4 to a time t5, and the control signal S3 sent from the power control portion 13 is selected as the control signal Sc1 after the time t5.