To provide a head-up display device capable of reducing cost.

The head-up display device includes: a display element 22 emitting display light L; a reflection member 31 having a reflection layer 31b reflecting the display light L; and a case member 32 having a base 33 which has an aperture 33a facing a required part of the reflection layer 31b, and a protruding wall 34 formed at the base 33. The projecting wall 34 includes a pair of opposed walls 60 and 61 which are provided along a pair of side surfaces P1 and P2 of the reflection member 31 which face each other, and opposed while putting the reflection member 31 between. One opposed wall 60 has an elastic pressing part 60a for pressing the reflection member 31 against the other opposed wall 61 side, and the display light L reflected by the reflection member 31 is projected to a projection member 13 to perform display for an observer 14. In the head-up display device, a holding means 35 for engaging and holding a bottom wall 31c of the reflection member 31 is integrally provided in the case member 32.