A discharge lamp lighting device that includes: a DC/DC converter that converts a power supply voltage of a direct-current power supply into a desired direct current voltage; a smoothing capacitor that smoothes an output of the direct current voltage from the DC/DC converter; a DC/AC inverter that converts, into an alternating current voltage, the direct current voltage smoothed by the smoothing capacitor; and a starting circuit that has a resonant circuit composed of at least one capacitor and at least one inductor and supplies an output of the DC/AC inverter to a discharge lamp (La), in which, at a time of starting the discharge lamp (La), the discharge lamp lighting device alternately repeats a period (HF1, HF2) while a high frequency voltage is being outputted, in which the resonant circuit performs a resonant operation, and a period (FB1, FB2) maintained for several milliseconds while a square wave voltage remains constant is being outputted, and at a time of lighting the discharge lamp (La), applies a low-frequency square wave voltage to the discharge lamp (La) through the starting circuit, the discharge lamp lighting device comprising: a starting detection unit for detecting the starting of the discharge lamp (La) during the period (FB1, FB2) while the square wave voltage is being outputted; and a control unit for stopping the high frequency voltage or lowering a frequency of the high frequency voltage in a case where the starting of the discharge lamp (La) is detected, wherein the control unit determines whether or not a predetermined period has elapsed, and in a case where the starting of the discharge lamp (La) has been detected at least once, the predetermined period is extended so that a number of repetitions of a period while the high frequency voltage and the square wave voltage are being outputted alternately is increased. a DC/DC converter that converts a power supply voltage of a direct-current power supply into a desired direct current voltage; a smoothing capacitor that smoothes an output of the direct current voltage from the DC/DC converter; a DC/AC inverter that converts, into an alternating current voltage, the direct current voltage smoothed by the smoothing capacitor; and a starting circuit that has a resonant circuit composed of at least one capacitor and at least one inductor and supplies an output of the DC/AC inverter to a discharge lamp (La), in which, at a time of starting the discharge lamp (La), the discharge lamp lighting device alternately repeats a period (HF1, HF2) while a high frequency voltage is being outputted, in which the resonant circuit performs a resonant operation, and a period (FB1, FB2) maintained for several milliseconds while a square wave voltage remains constant is being outputted, and at a time of lighting the discharge lamp (La), applies a low-frequency square wave voltage to the discharge lamp (La) through the starting circuit, the discharge lamp lighting device comprising: a starting detection unit for detecting the starting of the discharge lamp (La) during the period (FB1, FB2) while the square wave voltage is being outputted; and a control unit for stopping the high frequency voltage or lowering a frequency of the high frequency voltage in a case where the starting of the discharge lamp (La) is detected, wherein the control unit determines whether or not a predetermined period has elapsed, and in a case where the starting of the discharge lamp (La) has been detected at least once, the predetermined period is extended so that a number of repetitions of a period while the high frequency voltage and the square wave voltage are being outputted alternately is increased. a starting detection unit for detecting the starting of the discharge lamp (La) during the period (FB1, FB2) while the square wave voltage is being outputted; and a control unit for stopping the high frequency voltage or lowering a frequency of the high frequency voltage in a case where the starting of the discharge lamp (La) is detected, wherein the control unit determines whether or not a predetermined period has elapsed, and in a case where the starting of the discharge lamp (La) has been detected at least once, the predetermined period is extended so that a number of repetitions of a period while the high frequency voltage and the square wave voltage are being outputted alternately is increased.