An optical unit and an image display device include a display element configured to emit imaging light, a first mirror having partial transparency and configured to reflect a portion of the imaging light emitted from the display element, and a second mirror configured to return the imaging light reflected by the first mirror to the first mirror to form an exit pupil. The imaging light is incident on the first mirror from the display element at a first incident angle, and the imaging light is incident on the first mirror at a second incident angle that is smaller than the first incident angle from the second mirror, and the first mirror includes an angle dependent separation film that shows different separation characteristics for the imaging light according to the difference between the first incident angle and the second incident angle.