A touch sensing system which senses a touch position on a screen, including a light source to emit light; a light deflection unit to deflect the light emitted from the light source, a light guide plate which is arranged opposite to the screen and guides the light deflected by the light deflection unit to different positions on the screen according to an incident position, a light detector to receive at least part of the light reflected in a touch position on the screen, and a controller to calculate the touch position on the screen based on a point of time when the light detector detects the light.