Head-up display device

A head-up display device comprising:

• a picture generation unit (PGU) configured to output an image;
• a first mirror disposed in front of the PGU along a frontward optical path and configured to change a path of the image, and configured to transmit at least a portion of a wavelength of light therethrough;
• a second mirror disposed in front of the first mirror along the frontward optical path, configured to pivot to between a first position and a second position, and configured to project the image while being at the first position and to block external incoming light while being at the second position;
• and
• a printed circuit board (PCB) on which at least one sensor is mounted, wherein the sensor measures an illuminance of the external incoming light incoming along a backward optical path opposite to the frontward optical path,
• wherein the at least one sensor is not positioned at a position of the PCB corresponding to a point of the first mirror which a chief ray generated from the PGU reaches, but is positioned at a position around the position of the PCB corresponding to the point of the first mirror which the chief ray reaches.