A display device includes a substrate, a plurality of pixel columns, and a lighting test circuit unit. The lighting test circuit unit is disposed in a non-display area on the substrate, includes a plurality of lighting test transistors, and provides a lighting test voltage to the pixel columns. Each of the lighting test transistors includes an active pattern including a source area, a drain area, and a channel area, a gate electrode disposed in the channel area, an interlayer insulating layer including a first contact hole spaced apart from a first side of the gate electrode by about 7 um or more, and a source electrode contacting the source area of the active pattern through the first contact hole.