A high-pressure discharge lamp operating device is capable of maintaining a start pulse voltage within a specific value by feeding back the start pulse voltage and making it constant even when the output capacity increases because of an output wiring length increase. A high-pressure discharge lamp operating device comprising a high pressure discharge lamp (8), a start pulse generating circuit (7)for supplying a starting high voltage to the high-pressure discharge lamp (8), and a control circuit (9) for controlling the start pulse generating circuit (7) is characterized in that the start pulse generating circuit (7) comprises a transformer (T1) for stepping up the pulse voltage generated by turning on/off a FET, a feedback voltage detecting winding (N3) provided in the transformer (T1), avoltage dividing circuit (11) for dividing the voltage generated in the feedback voltage detecting winding (N3), and a pulse detecting circuit (12) for detecting a start pulse voltage component from the output of the voltage dividing circuit (11) and feeding back the start pulse voltage component to the control circuit (9), and that the control circuit (9) maintains the start pulse voltage stepped up by the transformer (T1) at a predetermined value.