PURPOSE: To provide a discharge lamp lighting device in which discharge can be stabilized when a discharge lamp is DC-lighted.

CONSTITUTION: This device has a DC power source circuit 22 for supplying a DC power to a discharge lamp 10, and a voltage detecting circuit 3 for outputting a detection signal when discharge is unstable after arc transition. When the detection signal from the circuit 5 is received, a discharge direction changing circuit 5 reverses the polarity of the DC power source applied to the discharge lamp 10 and changes the discharge direction at least once or more.