A vehicle display device includes a display that emits a display image to be projected onto a windshield provided to a vehicle, as display light, at least one reflecting mirror that is disposed on an optical path of the display light from the display to the windshield and reflects the display light, an optical sensor that detects external light (SL) incident from an opening through which an outside and an internal space are communicated with each other, a temperature sensor that detects a temperature of the display, a dimming member that is disposed on the optical path of the display light, and a controller that causes the dimming member to be switched between a state with a first transmissivity and a state with a second transmissivity smaller than the first transmissivity.