An in-plane switching mode liquid crystal display device includes: a lower substrate and an upper substrate which face each other; a gate line and a data line on the lower substrate such that the gate line and the data line cross each other to define a pixel region that is divided into a transmissive region and a reflective region; a thin film transistor arranged at a crossing of the gate line and the data line; a reflective plate in the reflective region; a pixel electrode and a common electrode arranged in an alternating pattern at the pixel region; a retardation layer arranged on the upper substrate to correspond to the reflective region; a liquid crystal layer between the upper substrate and the lower substrate; and a first polarizing plate and a second polarizing plate at outer surfaces of the lower substrate and the upper substrate, respectively.