A backlight driving device for driving a backlight that illuminates a display panel is disclosed. The backlight driving device includes: a luminance data input device into which luminance data indicated by a video signal is entered; a drive signal-generating device configured to create a drive signal; a power supply device configured to supply electric power to the backlight according to the drive signal so as to drive the backlight; a video signal decision device configured to make a decision as to whether each value of the luminance data entered into the luminance data input device is smaller than a given value; and a thinning-out device configured to thin out components of the drive signal when the video signal decision device has determined that the value of the luminance data is smaller than the given value and supply the thinned drive signal to the power supply device.