A head-up display device projects a display light on a windshield of a vehicle to form a virtual image thereon. The device includes a casing, an indicator which is attached to the casing to emit the display light into the casing, a light guide path through which the display light emitted from the indicator is guided, and a wiring board which is provided with a driving circuit for driving the indicator. The casing includes a guide rail formed along an irradiation direction of the display light from the indicator to support both lateral portions of the wiring board on the guide rail, and the wiring board is attached in a containing space of the casing formed between the light guide path and an inner surface of the casing by guiding and sliding the wiring board along the irradiation direction of the display light with the guide rail.