An in-plane-switching-mode (IPS) LCD device includes a TFT substrate and a CF substrate sandwiching therebetween a liquid crystal (LC) layer, and a pair of polarizing films sandwiching therebetween the TFT and CF substrates and LC layer. The TFT substrate includes a SiNx insulation layer having a higher refractive index compared to the TFT substrate and LC layer. The thickness (d) of the SiNx layer is expressed by d=(100+170.times.k).+-.30 where k is an integer not smaller than zero and not larger than 5. The protective layer of the light-incident-side polarizing film near the insulation film has a thickness larger than zero and not larger than 57 .mu.m.