In order to achieve reduction in size, an image position adjustment device (1) includes a light source unit (3) which emits visible light and infrared light, a movable cold mirror (12) which reflects visible light and transmits infrared light, a second scanner mirror (13) which reflects infrared light transmitted through the movable cold mirror (12), a windshield glass (F) which displays an image with visible light reflected by the movable cold mirror (12), and a first image processing unit (5) which images the driver (D) using reflected light of infrared light reflected by the second scanner mirror (13) on the driver (D) to detect a line-of-sight position of the driver (D). The position of an image is adjusted in accordance with the line-of-sight position detected by the first image processing unit (5).