A lamp electrode printed circuit board of a backlight unit includes an insulating substrate, first and second conductive patterns on the insulating substrates along a first direction and in parallel, a connecting pattern extending from one of the first and second conductive patterns, a connecting pad at one end of the connecting pattern, auxiliary patterns extending from an edge of the connecting pad, and lamp holders electrically connected to the first and second conductive patterns and spaced apart from each other along the first direction.