A head-up display apparatus includes light emission units, a first reflection unit, a second reflection unit, a first diffusion unit, a second diffusion unit, and a driver unit. The light emission units are disposed along one end surface of an upper or lower end surface of a combiner, and emit light. The first reflection unit is disposed to a part of the light emission units, and reflects the light. The second reflection unit is disposed to a part of the light emission units, and reflects the light. The first diffusion unit is disposed in the first side end surface, and diffuses the light. The second diffusion unit is disposed in the second side end surface, and diffuses the light. The driver unit selectively drives one of the light emission unit, and causes to emit the light. The combiner includes an invisible region.