VIRTUAL IMAGE DISPLAY OPTICAL SYSTEM AND IMAGE DISPLAY DEVICE

An object of the present invention is to provide a virtual image display optical system that is capable of substantially simultaneously displaying virtual images at a plurality of distances even with a simple configuration, and an image display device using the virtual image display optical system. A virtual image display optical system () according to the present invention is provided with: a display element (); a projection optical system () that enlarges an image formed on the display element (); a diffusing screen () that has a diffusing function, and is positioned on the light emission side of the projection optical system (); and a virtual image forming optical system () that converts an image on the diffusing screen () into a virtual image, wherein the virtual image display optical system () is further provided with a positioning changing device () that changes a position of the diffusing screen ().