An IPS liquid crystal display device with a reduced number of layers, in which the variation of pixel electrode potential due to ON/OFF operation of a gate voltage is suppressed. A pixel electrode is formed on a TFT substrate formed of glass. A gate insulating film is formed to cover the pixel electrode, an inorganic passivation film is formed on the gate insulating film, and a common electrode is formed on the passivation film. A liquid crystal molecule is driven with an electric line of force in a slit formed in the common electrode. A capacitive electrode, which is connected to the common electrode, is formed on the gate insulating film. The capacitive electrode forms an added capacitance with the pixel electrode via the gate insulating layer. The variation of pixel electrode potential due to ON/OFF operation of a gate voltage is suppressed with the added capacitance.