The invention relates to a vehicle-mounted head-up display device. The vehicle-mounted head-up display device comprises a fixing support used for installing a display device body, and a multi-narrow-spectrum-band high-reflection component arranged on a light outgoing path of the display device body and used for reflecting image information displayed by the display device body. The reflectivity of the multi-narrow-spectrum-band high-reflection component relative to at least two types of narrow spectrum light rays is larger than 50%, and the transmittance of the multi-narrow-spectrum-band high-reflection component relative to light rays except for the at least two types of narrow spectrum light rays is larger than 50%. Narrow-band spectrum light rays belong to the spectrum within the range from the central wavelength with 30 nm subtracted to the central wavelength plus 30 nm. The vehicle-mounted head-up display device is small in size and can be used both during the daytime and at night.