The present invention provides a backlight unit comprising a light source unit divided into a plurality of divisions which are driven independently each other, a light source driving group supplying electric power to the light source unit and comprising a multi-driving part which is connected to the divisions of at least two, and a light source controller controlling the light source driving group so as to selectively supply electric power to the divisions connected to the multi-driving part. The present invention also provides a method of controlling the backlight unit. Thus, the present invention provides a backlight unit and method for controlling a backlight unit comprising a light source unit which is divided into simple configurations and is efficiently driven.