A head-up display apparatus projecting an image onto a display region of a windshield and allowing a driver of a vehicle to visually recognize a landscape on which the image is superimposed, the head-up display apparatus comprising: a light source emitting light; a display panel creating an image to be projected onto the display region by modulating the light from the light source; a reflection mirror (M1, M2) reflecting the image created by the display panel to project it onto the display region; a solar radiation sensor detecting a sunlight intensity when a position of sun exists within a predetermined detection range; a blocking mechanism forming a projected light path of the image between the display region and the display panel when tuned OFF, and blocking the projected light path of the image and an incident light path of the sunlight which is a direction opposite to the projected light path when turned ON; a protection processor controlling ON / OFF of the blocking mechanism based on an estimated temperature of the display panel, the estimated temperature being estimated by using the sunlight intensity from the solar radiation sensor, luminance of the light source, and an ambient temperature; and a drive mechanism changing an installation angle of the reflection mirror (M1, M2), which is attached to the reflection mirror (M1, M2), wherein, when turned ON, the blocking mechanism blocks the incident optical path of the sunlight by changing the installation angle of the reflection mirror (M1, M2) via the drive mechanism, wherein a normal mode, a degenerate mode, a protective mode are provided as operational modes, in the normal mode the blocking mechanism being turned OFF and the luminance of the light source being not limited, in the degenerate mode the blocking mechanism being turned OFF and the luminance of the light source being limited to a value lower than that in the normal mode, in the protective mode the blocking mechanism being turned ON and drive of the light source being stopped, and wherein the protection processor controls the operational modes, characterized in that the protection processor is shifted from the protective mode to the degenerate mode when the sunlight intensity is in a state of a predetermined off-intensity or less and the state continues for a predetermined off-time. a light source emitting light; a display panel creating an image to be projected onto the display region by modulating the light from the light source; a reflection mirror (M1, M2) reflecting the image created by the display panel to project it onto the display region; a solar radiation sensor detecting a sunlight intensity when a position of sun exists within a predetermined detection range; a blocking mechanism forming a projected light path of the image between the display region and the display panel when tuned OFF, and blocking the projected light path of the image and an incident light path of the sunlight which is a direction opposite to the projected light path when turned ON; a protection processor controlling ON / OFF of the blocking mechanism based on an estimated temperature of the display panel, the estimated temperature being estimated by using the sunlight intensity from the solar radiation sensor, luminance of the light source, and an ambient temperature; and a drive mechanism changing an installation angle of the reflection mirror (M1, M2), which is attached to the reflection mirror (M1, M2), wherein, when turned ON, the blocking mechanism blocks the incident optical path of the sunlight by changing the installation angle of the reflection mirror (M1, M2) via the drive mechanism, wherein a normal mode, a degenerate mode, a protective mode are provided as operational modes, in the normal mode the blocking mechanism being turned OFF and the luminance of the light source being not limited, in the degenerate mode the blocking mechanism being turned OFF and the luminance of the light source being limited to a value lower than that in the normal mode, in the protective mode the blocking mechanism being turned ON and drive of the light source being stopped, and wherein the protection processor controls the operational modes, characterized in that the protection processor is shifted from the protective mode to the degenerate mode when the sunlight intensity is in a state of a predetermined off-intensity or less and the state continues for a predetermined off-time.