There is provided a touch screen system including: a sensor module including a light emitting unit configured to generate a light signal and a photo detection sensor configured to receive the light signal; a display panel including the sensor module; a front case including a reflection area configured to reflect the light signal generated from the light emitting unit to the photo detection sensor; and a back case connected to the front case with the display panel positioned therebetween. The front case is fixed and connected to the back case and the reflection area is placed at a predetermined position on the display panel.