A lighting device has a power-factor correction circuit 6, a step-down chopper circuit 8, a full-bridge circuit 10, control ICs for these circuits and a driving-voltage supply circuit 14. The supply circuit 14 supplies a driving voltage to the control ICs. The control IC outputs the on/off driving voltage to a switching element of the corresponding circuit 6 to 10. The lighting device also has a detector 16 and judgment equipment 18. The detector 16 detects the driving voltage supplied from the supply circuit 14. The judgment equipment 18 instructs the control ICs to start outputting the on/off driving voltages in the order from the control IC close to the power source 2 to the control IC close to the discharge lamp 4 when the driving voltage detected by the detector 16 reaches a predetermined value during the time when the driving voltage supplied from the supply circuit 14 rises.