PURPOSE: To provide a discharge lamp lighting device, in which the heat generation of element, deterioration of switching element, etc., are difficult to occur.

CONSTITUTION: After a discharge lamp FL is lighted, the voltage of the discharge lamp FL lowers so that the potential of the connection of resistors R8 and R9 lowers and an operational amplifier OP2 produces a non-inverted output. A chopper control circuit 9 controls the switching element Q1 of a booster chopper circuit 3, lowers the output of the booster chopper circuit 3 and lowers the output of an inverter circuit 4. After the discharge lamp FL is lighted, a lighting detector circuit 7 produces on output, turns ON a transistor Q4 and bypasses a current flowing through a voltage detector circuit 8. Even if the output of the voltage detector circuit 8 is lowered and the voltage of the discharge lamp FL rises, the current of the resistor R10 is not bypassed and the booster chopper circuit 3 is prevented from increasing output.