An array substrate for in-plane switching (IPS) mode liquid crystal display (LCD) device includes a gate line and a common line in a horizontal direction on a substrate, a data line crossing the gate line and the common line, a pixel electrode and a common electrode on the substrate, and a thin film transistor at a crossing point of the gate line and the data line, the thin film transistor having a gate electrode, an active layer and source and drain electrodes, the gate electrode having a slope that satisfies a numeral expression |θR−θg|=89°˜91° (degree) wherein θR is an angle of a rubbing direction measured from an arbitrary horizontal line and θg is an angle of the slope of the gate electrode measured from the arbitrary horizontal line.