A high-intensity discharge lamp operating device includes a power supplier configured to supply power to a high-intensity discharge lamp, a memory containing a starter power data set, an identifying power data set and steady power data sets, a detector configured to detect voltage applied to the high-intensity discharge lamp, a power supplier controller configured to control the power supplier to control the power according to the starter power data set, the identifying power data set and one of the steady power data sets, a lamp power identifier configured to identify a lamp power of the high-intensity discharge lamp while the power supplier controller controls the power according to the identifying power data set after the starter power data set, and a data set selection unit configured to select one steady power data set based on the identified lamp power, and the power supplier controller is configured to control the power according to the steady power data set.