An image input/output device 100 includes an image information detection section 130 for detecting image information of an image information object 200 by receiving reflected light L from the image information object 200, and a self-luminous image display section 120 for displaying an image based on the image information detected by the image information detection section 130. The image information detection section 130 and the self-luminous image display section 120 are attached together in a back-to-back arrangement. The self-luminous image display section 120 functions as an image-information-detecting light source for irradiating the image information object 200 with light L through the image information detection section 130.