A head-up display apparatus mounted on a moving body. The head-up display apparatus projects an image on a projecting portion. The head-up display apparatus includes a light source portion, an imaging element, a cold mirror, and a phase shifter. The light source portion emits a source light. The imaging element generates the image and outputs the light of the image. The light of the image has a predetermined polarization state. The cold mirror reflects the light of the image toward the projecting portion. In the cold mirror, an optical multilayer film is disposed on a translucent base member, and the light of the image obliquely enters the cold mirror along a plane of incidence of the cold mirror. The phase shifter converts the light of the image into an S wave. The phase shifter is disposed on an optical path between the imaging element and the cold mirror.