A discharge lamp driving device includes: a direct-current power supply section (a power supply section) that controls a current of power to be supplied to a discharge lamp from input power, and outputs the current; a voltage detecting section that detects a lamp voltage (a drive voltage) of the discharge lamp; and a control section that controls a modulation factor of a lamp current (a drive current) on which amplitude modulation has been performed, the lamp current (the drive current) which is supplied to the discharge lamp from the direct-current power supply section (the power supply section), in accordance with the detected lamp voltage (drive voltage) of the discharge lamp.