Output of a chopper circuit is converted to a rectangular wave by a push-pull circuit, and is provided to a step-up transformer. When a switch is turned on, the control voltage of the chopper circuit is relatively low, and a high output voltage is provided to the transformer. Thus, the discharge lamp starts with certainty. When the discharge lamp starts, the transistor is turned on, and the resistance generating the control voltage is connected in parallel to other resistance, and the control voltage is increased. Thus, the output of the chopper circuit is decreased, and thereafter becomes a constant voltage. Thus, the dielectric barrier discharge lamp is started with certainty, and also is driven with stability.