A electronic ballast includes an inverter circuit for converting a DC voltage into a high-frequency voltage, a resonant circuit connected between outputs of the inverter circuit so as to light a discharge lamp by a resonant action, a control circuit for controlling the inverter circuit, a dimming circuit for continuously changing an output voltage to the discharge lamp by changing an operation frequency in the inverter circuit, a DC component detection circuit and a voltage comparator for detecting whether or not the discharge lamp is at the end of the life at predetermined intervals and outputting an end of life detection signal upon detection of the end of the life state, and a frequency control circuit and a driving circuit for reducing or stopping an output to the discharge lamp by controlling switching elements in response to a life end detection signal inputted from the voltage comparator.