A head-up display device comprises a reflective mirror mounting bracket having an accommodation space; a reflective mirror arranged on the reflective mirror mounting bracket, receiving a real image and reflecting the real image to generate a reflected image; and a concave imaging mirror mounting bracket accommodating a concave imaging mirror, wherein the concave imaging mirror is coated with an antireflection film on one side and coated with a semi-transmitting film on the other side, reflects the reflected image of the reflective mirror and presents a distant magnified virtual image. The present invention is characterized in a small size; no need to install the device inside the instrument panel system; directly using an existing display device to generate a distant magnified virtual image; and easiness for users to install the device.