A lighting device for a high intensity discharge lamp (La) comprising: a direct current power source; a down-converter circuit configured to step down a direct current voltage supplied from the direct current power source; a polarity inversion (inverter) circuit configured to receive an output voltage from the down-converter circuit and apply the output voltage to the high intensity discharge lamp (La) with a polarity of the output voltage inverted periodically; a resonance circuit configured to generate a starting voltage for starting up the high intensity discharge lamp (La); a control circuit (410, 420) configured to control the down-converter circuit, the polarity inversion (inverter) circuit, and the resonance circuit to control lighting of the high intensity discharge lamp (La); voltage detecting means for detecting the output voltage from the down-converter circuit configured to step down the direct current voltage; the lighting device is characterized by further comprising lighting detection means for detecting a state of output of the polarity inversion (inverter) circuit, and the lighting detection means is configured to detect lighting and extinction of the high intensity discharge lamp (La) and to detect, during a period of detecting lighting of the high intensity discharge lamp (La), an asymmetric state in a current in the high intensity discharge lamp; and wherein the control circuit is configured to determine the output voltage from the down-converter circuit on a basis of the output voltage from the down-converter circuit detected by the voltage detecting means and the state detected by the lighting detection means, wherein the control circuit is configured to reduce the output voltage from the down-converter circuit, when the asymmetric state is detected by the lighting detection circuit. a direct current power source; a down-converter circuit configured to step down a direct current voltage supplied from the direct current power source; a polarity inversion (inverter) circuit configured to receive an output voltage from the down-converter circuit and apply the output voltage to the high intensity discharge lamp (La) with a polarity of the output voltage inverted periodically; a resonance circuit configured to generate a starting voltage for starting up the high intensity discharge lamp (La); a control circuit (410, 420) configured to control the down-converter circuit, the polarity inversion (inverter) circuit, and the resonance circuit to control lighting of the high intensity discharge lamp (La); voltage detecting means for detecting the output voltage from the down-converter circuit configured to step down the direct current voltage; the lighting device is characterized by further comprising lighting detection means for detecting a state of output of the polarity inversion (inverter) circuit, and the lighting detection means is configured to detect lighting and extinction of the high intensity discharge lamp (La) and to detect, during a period of detecting lighting of the high intensity discharge lamp (La), an asymmetric state in a current in the high intensity discharge lamp; and wherein the control circuit is configured to determine the output voltage from the down-converter circuit on a basis of the output voltage from the down-converter circuit detected by the voltage detecting means and the state detected by the lighting detection means, wherein the control circuit is configured to reduce the output voltage from the down-converter circuit, when the asymmetric state is detected by the lighting detection circuit.