A discharge lamp operating apparatus including: a discharge lamp; an operating circuit; a voltage measuring unit; a magnetic field applying unit; and a control unit, wherein the voltage measuring unit measures the voltage of power at sampling intervals, the control unit calculates an average value VL1 of a group of the measured value of the voltage as a standard and an average value VL2 of a group of the measured value of the voltage for comparison after a predetermined time has elapsed from the measurement of the measured value of the voltage measured at the beginning from the group of the measured value of the voltage as a standard, and when the difference (VL2−VL1) between the average value VL1 and the average value VL2 exceeds a predetermined value, drives the magnetic field applying unit.