A touch screen apparatus includes a mirror part arranged on a side of a quadrilateral touch area, retroreflectors arranged on remaining three sides of the touch area, first and second light transmitting and receiving parts, each being disposed on each of two edges formed by one of the retroreflectors and emitting light to the touch area and detecting reflected light out of the emitted light by the mirror part and the retroreflectors, an angle extracting part calculating a plurality of light emitting angles for a location from which no reflected light is received, by at least one of the first and second light transmitting and receiving parts, and a coordinate generating part calculating a coordinate pair of a location in which light paths corresponding to the plurality of light emitting angles calculated by the angle extracting part intersect with each other.