An image-pickup display device includes an optical system which guides lights from a display element 1 to an exit pupil 3 and from an external to an image-pickup element 2. The optical system includes an optical element 10 which is filled with a medium having a refractive index larger than 1. The optical element includes a first surface 7 at an external side and includes a diffraction element portion 13. The optical system guides the light from the display element to the exit pupil via reflection on a second surface 5 and the first surface and via transmission on the second surface, and diffracts the light from the external in the diffraction element portion to be transmitted through the first surface to enter the optical element, and is reflected on the second surface to be transmitted through a third surface 5 to be guided to the image-pickup element.