Provided are a directional backlight unit and an image display apparatus including the same. The directional backlight unit includes at least one light source, a light guide plate arranged at a side of the at least one light source and configured to guide light emitted from the at least one light source by total reflection, a plurality of diffraction gratings arranged in a pattern at a surface of the light guide plate and configured to diffract the light and to emit the light diffracted by the plurality of diffraction gratings at a predetermined angle from a front surface; and a mirror arranged at a rear surface of the light guide plate and configured to reflect the light diffracted by the plurality of diffraction gratings toward the light guide plate, the rear surface of the light guide plate being opposite to the front surface of the light guide plate.