Head-up display control system and head-up display display method

A head-up display control system comprising:

• a head-up display device that is installed in a vehicle and displays display information in a position overlapping with a window;
• a terminal holder installed in the vicinity of the window in a vehicle interior;
• a mobile terminal installation detection unit that detects whether a mobile terminal is installed on the terminal holder;
• and
• a control unit that controls the head-up display device,
• wherein
• the head-up display device includes a display position change unit that changes a display position of the display information, and
• the control unit changes the display position from a first display position to a second display position when the installation of the mobile terminal is detected by the mobile terminal installation detection unit,
• in a case where the mobile terminal is installed on the terminal holder, an area of a holder projection region obtained by projecting the terminal holder onto a plane parallel to a display screen of the mobile terminal is smaller than an area of a terminal projection region obtained by projecting the mobile terminal onto the plane,
• the first display position is a position that does not overlap with the holder projection region in a vehicle front-and-rear direction but overlaps with the terminal projection region, and
• the second display position is a position that does not overlap with the holder projection region or the terminal projection region in the vehicle front-and-rear direction.