An in-plane switching mode liquid crystal display device includes a first substrate and a second substrate, a gate line and a data line crossing each other on the first substrate to define a pixel region, a switching device at a crossing of the gate line and the data line, a pixel electrode and a common electrode on the first substrate for generating an in-plane electric field in the pixel region, a black matrix, a light blocking line, the light blocking line being below the black matrix and above the data line, the light blocking line covering a gap between the data line and the common electrode adjacent to the data line, and a liquid crystal layer formed between the first and second substrates.