PURPOSE: To provide a stabilized DC power supply device for discharge lamp, which allows enhancement of the lighting performance immediately after starting of lamp lighting.

CONSTITUTION: A polarity inversion preventing means 10 prevents inversion of the polarity of the output voltage (v) of a chopper circuit 2 immediately after the starting of lamp lighting with electric vibration of a transformer T1 and smoothing capacitor C1. Even immediate after the start of lamp lighting, therefore, power is supplied continuously to the discharge lamp 6, so that the lamp current (i) does not nullify to lead to prevention of stall of lamp lighting and also the polarity of the output voltage (v) of the chopper circuit 2 does not make inversion, which precludes risk of a malfunction of control circuit 5.