An image display device includes an image generating device, a light guide unit, and a light beam expanding device. The light guide unit includes a light guide plate, a first deflector, and a second deflector. The light beam expanding device expands a light beam incident from the image generating device along the Z direction and outputs the light beam to the light guide unit when the incident direction of light incident on the light guide plate is defined as the X direction and the propagation direction of light in the light guide plate is defined as the Y direction. The light beam expanding device is composed of a first reflective mirror on which light from the image generating device is incident and a second reflective mirror on which light from the first reflective mirror is incident and that outputs light to the light guide unit.