Abstract: A discharge lamp lighting device in which dim control can be performed for a discharge lamp continuously and stably in a wide range, and which is simple in circuit configuration and low in price. The discharge lamp lighting device comprises: an inverter (IV) for turning on/off switching elements (Q2, Q3) by an oscillation output signal of an IV control integrated circuit (IC2) to thereby invert a voltage of a DC power supply (E) into high-frequency electric power, a discharge lamp (LA) capable of being lighted by the high-frequency electric power from the inverter (IV), a feedback circuit (FB) having delay time T (unit: second) expressed by 1/f≦T≦1/10,000 when the frequency of the high-frequency electric power is f, the feedback circuit (FB) including a reference value setting means (R15) for setting a reference value, the feedback circuit outputting a voltage for controlling the IV control integrated circuit (IC2) to make the high-frequency electric power equal to the reference value.