A lamp driving device includes a switch circuit for supplying a signal; a transformer which boosts a voltage of the signal from the switch circuit and supplies the boosted voltage to at least one lamp; a safety circuit which compares a threshold value with at least one of the boosted voltage and a current through the lamp, and intercepts at least one of the boosted voltage and the current through the lamp in accordance with the comparison result; and a warming part for warming the lamp in an early stage with a voltage less than or equal to the threshold value.