A line of sight detection system includes a light source that emits light toward a subject, a light detector configured to detect reflected light from the subject, a control unit configured to change an emission pattern of the light emitted from the light source toward the subject, an identification unit configured to identify a line of sight position of the subject based on a change of the reflected light from the subject when the emission pattern of the light is changed, and an output unit configured to output information of the line of sight position.
