To solve such a problem of a liquid crystal display device that an afterimage remains in displaying moving images.

A backlight control method includes the steps of: dividing the screen of a liquid crystal display device into a plurality of regions; detecting the time when image information is written in a divided region; reducing the luminance of the backlight in the divided region when the time of writing the image information is detected; judging the time when displaying the image information written in the divided region is established; and raising the luminance of the backlight in the divided region when displaying the image information is established.