To easily adjust the contrast of a liquid crystal display device with flexibility.

This system is equipped with a tilt angle detecting circuit 2 which detects the tilt angle of the liquid crystal display plate 1, a contrast control part 4 which receives the detected tilt angle and automatically adjusts the contrast of the display screen of the liquid crystal display device 1 according to the tilt angle, a storage part 3 having a contrast setting table 14 which can be rewritten corresponding to the tilt angle of the liquid crystal display plate 1, and a setting operation part 6 which instructs the contrast control part 4 to vary and set a contrast set value in the contrast setting table in response to user's operation.