This study describes the depth perception in a moving vehicle when using an automotive 3D Head-Up Display which places virtual images in the appropriate 3D position. In the experiment, we compared the 3D-HUD with a conventional augmented reality HUD, which has fixed focal depth, in terms of visibility. The visual contents were displayed in various distances. Participants were instructed to answer how deep the displayed content indicated while performing the visual task. Judgement time and error were measured during the experiment. Based on the results, we discussed how the driver's depth perception was influenced by image position and vehicle traveling.