A head-up display device includes a housing, a base, a projecting board assembly, a protecting cover and a driving mechanism. The projecting board assembly has a holder and a projecting board. The protecting cover is movably arranged on the projecting board assembly, and can be used to cover the projecting board or uncover to expose the projecting board. The projecting board assembly is rotatably arranged above the base by the driving mechanism, and the driving mechanism can drive the projecting board assembly at a storing position or a displaying position. The driving mechanism can drive the protecting cover to be guided by the first guiding mechanism, so as to move the protecting cover. Otherwise, the driving mechanism can pull down the protecting cover by the second guiding mechanism to expose the projecting board, and make the projecting board assembly in the displaying position.