A method of eye tracking includes: irradiating a light pattern, output from at least one collimated light source, to a cornea surface; detecting at least a part of the light pattern reflected from the cornea surface, the at least the part of the light pattern being guided by a sensor waveguide; obtaining a mapping image corresponding to the at least the part of the light pattern; and determining a direction of a gaze based on the obtained mapping image. The sensor waveguide used to determine the direction of the gaze is different from a waveguide for displaying output information.