To provide a vehicle-mounted display device capable of easily preventing reflection of an image.

The vehicle-mounted display device 100 according to one aspect an embodiment of the present invention is the vehicle-mounted display device provided with a display panel 101 which can be directly visually recognized by a driver in the front visual field of the driver and which is provided at the position where the image reflected by a windshield 104 can be indirectly seen. The display panel 101 includes a polarizer provided on the visual recognition side. A retardation plate 103 is provided on the visual recognition side of the polarizer. The light emitted from the retardation plate 103 and directed toward the windshield 104 is the P polarized light whose oscillation direction is included in the incident plane and whose incident angle is near the Brewster angle.