An electronic ballast is capable of inhibiting ballast shutdown caused by erroneously determining a fault condition. The ballast includes a DC power supply circuit for outputting DC power, a power conversion circuit that appropriately converts DC power outputted by the DC power supply circuit and outputs it to a discharge lamp, a DC voltage droop detection circuit for determining existence/absence of a fault condition in the DC power supply circuit 1, a lamp end of life detection circuit for determining existence/absence of a fault condition of the discharge lamp; and a sequence control circuit and a shutdown control circuit that control at least the power conversion circuit according to detection by the DC voltage droop detection circuit the discharge lamp life detection circuit. When a fault is determined in both the DC voltage droop detection circuit and the discharge lamp life detection circuit, an operation according to the detection of the DC voltage droop detection circuit, the sequence control circuit lowers the output of the power conversion circuit 2 is performed in priority to an operation that, according to the detection of the discharge lamp life detection circuit, the shutdown control circuit shuts down the power conversion circuit